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The symbols of the sciences: physical quantities and constants, chemical and biological notation, units, and the Greek letters that carry most of them.
Here when the symbol denotes a quantity, a constant or an entity in a scientific discipline. Where a letter denotes different things in different fields, the record says so rather than picking one.
Officially standardised, largely through ISO 80000 and IUPAC, and then used far more loosely than those standards allow. Several records exist to record that difference.
All 747symbols in this domain, A–Z.
A capital M giving intrinsic brightness.
A capital K with a lowercase a subscript.
An italic capital S, the integral of the Lagrangian over time.
A Greek gamma, correcting concentration to effective concentration.
A marked opening driven horizontally into a hillside.
A raised star marking a conjugate transpose or dual.
An italic capital Y, the reciprocal of impedance.
A plus sign beneath a letter, marking a fronter articulation.
A sign for the vessel in which substances are melted at high heat.
A sign for a round vessel with a long downward-bent neck.
An upward triangle crossed by a horizontal bar.
A sign for the distilling head, the characteristic alchemical vessel.
A circle with a cross above it, the inversion of the sign for Venus.
A sign for nitric acid.
A sign for the acid mixture that dissolves gold.
A pair of overlapping triangles, or a stylised S-and-Z form depending on the source.
A sign for bismuth, one of the later metals to be distinguished.
A sign for reducing a substance to powder by strong heat.
A sign for mercury sulphide, the chief ore of mercury.
A sign for a liquid setting into a solid.
A sign for taking a solid into solution.
A sign for separating substances by boiling and condensing.
A downward triangle crossed by a horizontal bar.
A sign for the working of a substance from within.
An upward-pointing triangle, the alchemical sign for fire.
A sign for making a volatile substance stable against heat.
A sign for saltpetre, potassium nitrate.
A sign for phosphorus, isolated from urine in 1669.
A sign for controlled decay, held to precede regeneration.
A form resembling a crossed or looped stroke, denoting ammonium chloride.
A circle divided by a horizontal line through its middle.
A sign for a solid passing directly to vapour and back.
A triangle above a cross, the sign for sulphur and for the principle of combustibility.
A sign for a water bath, giving gentle and controlled heat.
A looped form resembling a script V or a hooked stroke, denoting sulphate salts.
A downward-pointing triangle, the alchemical sign for water.
A capital F marking points on every face.
Fine sorted material marking river deposits.
The first Greek letter, used across science for angles, rates and particles.
A capital H with a subscript one, naming the hypothesis accepted if the null is rejected.
A patterned mid-level layer of rounded cloudlets.
An upside-down r, for the r sound of English red.
An exclamation-mark shape, for a sharp popping click.
The letter l, used in phonetic transcription for an l sound.
A double vertical stroke, for a lateral click.
A letter r without its upper arc, for a single flapped r.
The letter r, used in phonetic transcription for a rolled r.
A capital A, the SI unit symbol for the ampere.
A fixed frame for the body.
A small wedge open to the right, prefixing the name of an angle.
A capital A with a small ring above it, marking a length of 10⁻¹⁰ metres.
A Greek omega, radians per second rather than cycles per second.
A capital L, rotational momentum about an axis.
A plain lowercase a, removing one quantum.
A Greek alpha or beta — a small curved letter — before a sugar's name.
An overbar marking a particle's antimatter counterpart.
Standard outlines for flasks, condensers and joints.
Two stacked wavy strokes, meaning 'roughly equal to'.
The letters aq in brackets after a formula.
A fixed point all measurements refer to.
A marked point locating an object.
Short strokes showing a cut edge.
A bounded area of excavation.
A raised letter h marking a puff of air.
Coordinate ranges bounding the smallest unique part.
A name and a date after a species.
A capital N with subscript A, the number of entities in a mole.
A dashed line marking a glide along an axis.
A unit of area for nuclear reaction probability.
An italic capital B, one third per quark.
Angular marks marking a fine-grained lava.
Alternating long and short parallel lines, marking a cell or battery.
A Greek letter with a constellation's genitive name.
A straight-sided cylinder with a pouring lip.
Wind force 0 to 12, described by what it does rather than measured.
The two letters Bq, the SI unit symbol for the becquerel.
A circle inside a hexagon, standing for delocalised electrons.
A hexagon with an inscribed circle, representing delocalised aromatic bonding.
The second Greek letter, used for beta particles, coefficients and angles.
A capital O with a bracketed expression, bounding a growth rate from above.
A circle with a central dot, for a lip-smacking click.
A small capital B, for a trill made with both lips.
A trefoil of overlapping circles, designed to be instantly recognisable as a warning for biological hazards.
A number from one to four rating containment.
A line with two angled leads inside a circle, one carrying an arrow.
A capital I marking a lattice point at the cell centre.
A Greek mu with a capital B subscript, the electron's magnetic unit.
An italic a with a nought subscript, the atomic length scale.
A wider tube for heating larger quantities.
An italic k, often subscripted B, relating temperature to energy.
A marked point recording where the ground was drilled.
Angle brackets and a bar denoting quantum states.
Four figures used for hexagonal crystals.
Two dots beneath a letter, marking breathy voice.
A theta with a B subscript, the angle of complete polarisation.
A Greek mu with a raised numeral, before a ligand's name.
A flat perforated plate above a stem.
A vertical barrel on a base with a gas inlet.
A long graduated tube with a tap at its foot.
A closed line with hachures marking a collapsed crater.
The two letters cd, the SI unit symbol for the candela.
Two parallel lines across a break in a wire, marking a capacitor.
Digits in three hyphen-separated groups, the last a single check digit.
A formula written above a reaction arrow, naming a catalyst.
A single upright stroke, marking a phase boundary.
Two dots above a letter, marking a central articulation.
A capital C, swapping every particle for its antiparticle.
A Greek mu, the energy cost of adding one more particle.
A Greek letter chi raised to the power two, naming a distribution and its test.
A branching incised channel figure.
Clustered closed depressions.
A capital gamma with one raised and two lowered indices.
Letters p and q naming the two arms.
Numbers locating a band on an arm.
A del with bracketed position.
An inv with bracketed breakpoints.
A t with bracketed chromosomes and breakpoints.
Fine curved streaks marking high ice cloud.
Plane indices naming a preferred break.
A strike line with a tick, for a plane of splitting.
The letter u, for the vowel of English goose.
A turned m, for a high back unrounded vowel.
A barred u, for a high central rounded vowel.
A barred i, for a high central vowel.
The letter y, for the vowel of French tu.
The letter i, for the vowel of English fleece.
The letter o, for the vowel of French eau.
A ram's horns shape, for an unrounded back vowel.
A barred o, for a close-mid central rounded vowel.
A reversed e, for a close-mid central vowel.
A slashed o, for the vowel of French peu.
The letter e, for the vowel of French ete.
How much of the station circle is filled — eighths of the sky.
A solid band marking a coal seam.
A Greek mu, the ratio of friction to normal force.
A line with solid triangles along one side, marking advancing cold air.
A small disc trailing a set of diverging lines.
An italic capital Z, one for an ideal gas and not otherwise.
A dotted fault line beneath younger cover.
Square brackets around a species, meaning its concentration.
A capital P with two events separated by a vertical bar.
A Greek sigma, the reciprocal of resistivity.
A pair of bounds, giving a range of plausible values for an estimate.
Rounded pebble shapes marking a conglomerate unit.
Three stacked horizontal bars, marking congruence rather than equality.
A cone-shaped vessel with a narrow neck.
A small circle with a short stroke rising from its right side.
Three letters standing for one of eighty-eight constellations.
A line marking air streams meeting and rising.
A lower-case r, reporting how closely two variables move together.
A capital Greek lambda, the energy of empty space.
Three capitals together, a symmetry believed exact.
A tilde beneath a letter, marking creaky voice.
A lowercase a with a dagger superscript, adding one quantum.
A theta with a c subscript, beyond which light cannot escape.
A figure limiting fissile packages carried together.
A Greek sigma, an effective target area for a reaction.
A lettered line marking where a section is drawn.
A descriptive term for external shape.
Names and axis descriptions classifying a crystal's symmetry.
Three figures in angle brackets naming equivalent directions.
Three figures in square brackets naming a direction.
Three figures in curly brackets naming equivalent planes.
A symbol naming one of thirty-two symmetry classes.
A heaped cloud drawn with a spreading anvil top.
A domed shape on a flat base, marking heaped fair-weather cloud.
A curved arrow showing where a pair of electrons moves.
A bold capital J, current per unit cross-section.
Small capital D or L before a name, from a sugar's Fischer projection.
A square operator combining space and time derivatives.
A Greek lambda, the probability per second of one nucleus decaying.
The two letters dB, marking a ratio on a logarithmic scale.
A celestial coordinate measured in degrees north or south.
A degree sign followed by a capital C, marking a temperature in Celsius.
A degree sign followed by a capital F, marking a temperature in Fahrenheit.
A small raised circle marking degrees of temperature, angle or arc.
The letters df, or a Greek nu, counting the values free to vary.
The fourth Greek letter, meaning change or difference in almost every field.
A Greek rho with a circumflex, a state that may be a mixture.
A single vertical stroke, for a tutting click.
A small bridge beneath a letter, marking tooth contact.
A Greek kappa with a raised numeral, before a ligand's name.
A sealed vessel with a plate above a drying agent.
Straight vertical bars around a square grid, denoting its determinant.
A dash-dot line marking a diagonal glide.
A stroke through a square or circle meaning the person has died.
A dash-dot line with arrows for a quarter glide.
A triangle pointing at a bar, marking a diode.
A capital D, optical power as a reciprocal metre.
A T-shaped piece carrying a thermometer.
A horizontal stroke with a dot above and below, indicating division.
Two strands winding around each other, joined by rungs.
Two parallel lines between atoms, representing a shared double bond.
A dagger with two crossbars, raised after a quantity.
Two parallel lines joining a couple who are blood relatives.
A capital letter suffix naming a component.
A downward arrow marking a lowered pitch register.
A fine line marking a cut watercourse.
Commas standing for drops too small to be rain.
An elongated oval marking an ice-moulded hill.
Letters naming which side of a double bond groups sit on.
A circle quartered by a cross — the Earth.
A number on a logarithmic scale, subscripted by method.
Twelve views, named by convention.
Codes naming an eclipse's type, date and magnitude.
A capital G with two indices, the geometry side of the field equations.
A raised apostrophe marking an ejective consonant.
A bold capital D, the electric field with polarisation folded in.
A script capital E, and not a force at all.
A numeral, a lowercase letter and a raised count, repeated.
An italic lower-case e, the magnitude of the charge on a proton.
A circle crossed by a diagonal stroke, denoting the set with no members.
A capital delta before an H, denoting heat absorbed or released.
An italic capital H, internal energy plus pressure times volume.
An italic capital S, a measure of how many ways a state can be arranged.
A letter and year fixing a coordinate frame.
The fifth Greek letter, conventionally a very small positive quantity.
A figure of eight on a dial.
Two half-headed arrows pointing opposite ways, marking a reversible reaction.
A winding ridge marking a subglacial stream bed.
A shallow open dish for driving off liquid.
A star name with a lower-case letter.
A capital E with a variable in brackets, meaning the long-run average.
A vertical stem with a mark at the top, for the highest pitch.
A vertical stem with a mark at the foot, for the lowest pitch.
A small breve above a letter, marking a very short sound.
A capital F, the SI unit symbol for the farad.
An italic capital F, the charge on a mole of electrons.
A heavy line with ticks or arrows showing which side moved.
Two digits: quadrant then tooth.
Lines that stand for an integral.
Straight, wavy and coiled lines for different particles.
A shaded square or circle: this person has the condition being traced.
A Greek alpha for a pure number near one over one hundred and thirty-seven.
A crescent opening to the left, marking the waxing half moon.
A cross of straight lines with the vertical bonds going back.
A number with a constellation name.
Square brackets with the top or bottom serifs removed, marking rounding direction.
An italic f, the distance from a lens to its focus.
Three stacked horizontal lines marking visibility below a kilometre.
An arrowed line showing where rock has been bent.
A strike line with a tick, for a metamorphic fabric.
An inverted capital A, the universal quantifier of formal logic.
A circled plus or minus on an atom in a structure.
A filled square marking a fourfold axis.
Three fractions locating an atom in a cell.
Blue for cold, red for warm, purple for occluded — where colour is available.
An italic f, an effective pressure for a real gas.
An enclosure with a sliding sash and extraction.
A rectangle with a line through it, marking a fuse.
The third Greek letter, used for gamma rays, functions and display response.
An italic capital R, the molar gas constant.
An upward arrow after a formula, marking a gas leaving the reaction.
A graduated barrel with a free-moving plunger.
Italics for the gene, upright for the protein.
Colours standing for the age of the rock beneath.
Letters printed on a map naming the rock's age.
An image of a substance corroding a surface and a hand, in a red-bordered diamond — the GHS symbol for corrosive hazard.
A black image of a dead fish and tree in a red-bordered diamond, the GHS symbol for aquatic/environmental hazard.
A black exclamation mark in a red-bordered diamond, the GHS symbol for lower-level health/physical hazards or irritation.
A black exploding-bomb icon in a red-bordered diamond, the GHS symbol for explosive hazard.
A black flame above a black circle in a red-bordered diamond, the GHS symbol for oxidizing hazard.
A black flame icon in a red-bordered diamond, the GHS symbol for flammable hazard.
A black gas cylinder icon in a red-bordered diamond, the GHS symbol for gases under pressure.
A capital H followed by three digits.
A black human silhouette with a starburst on the chest, in a red-bordered diamond — the GHS symbol for serious, longer-term health hazards.
A capital P followed by three digits.
A black skull and crossbones in a red-bordered diamond, the GHS symbol for acute toxicity.
An italic capital G, deciding whether a reaction proceeds.
A line marking scratches cut by moving ice.
A falling arrow marking falling intonation.
A rising arrow marking rising intonation.
A question mark without its dot, for a catch in the throat.
A lowercase g, the carrier of the strong force.
Banded lines marking a coarsely foliated rock.
A narrow tube with a scale along its length.
Crosses and dashes marking a coarse igneous rock.
An italic capital G, the constant in Newton's law of gravitation.
A contour of gravitational variation.
An angle bracket opening to the left, stating that the left value is larger.
A greater-than wedge with a bar beneath it, allowing equality as well.
A triangle with a dot, marking ice pellets from a storm.
A single triangle marking a half-long sound.
A t with subscript one-half, the time for half a quantity to decay.
A scripted or hatted H standing for a system's total energy.
A Greek eta with a raised numeral, before a ligand's name.
A number for how cold it gets.
A diagram of stratigraphic relationships in an excavation.
A boxed context number in a diagram.
A line stating which context is earlier.
A ladder of short lines showing a bond going away.
A caret over a letter, marking an estimate or a unit vector.
A flat ring drawn in perspective with substituents up or down.
An angular infinity-like mark for suspended dry particles.
A line of small marks along a field boundary.
An italic capital A or F, the constant-volume counterpart of Gibbs energy.
The letters HD with a number.
A slip that revises a name.
Symmetry named by axis order and plane letter.
The two letters Hz, the SI unit symbol for the hertz.
A capital H, the excitation of the field that gives mass.
A capital H or L at the middle of a set of closed isobars.
A vertical stem with a mark high on it, for a high pitch.
Carbon first, hydrogen second, then everything alphabetically.
A cross in a circle marking undipped strata.
A capital H with a nought subscript, the current expansion rate.
A double-shafted arrow with heads at both ends, denoting logical equivalence.
An italic capital Z, resistance extended to alternating current.
A double-shafted arrow pointing right, denoting logical implication.
A structured string beginning InChI= with slash-separated layers.
A doubled upright stroke pair, denying any statistical relation.
The letters IC with a number.
A row of humps or a filled rectangle in a wire, marking an inductor.
A dashed fault line whose existence is deduced.
An elongated S indicating integration in calculus.
An inverted rounded U, denoting what two sets have in common.
Mixed square and round brackets marking whether an endpoint is included.
A small open circle marking a centre of symmetry.
Year, month and day in fixed order, largest unit first.
A line joining points of equal air pressure on a weather chart.
Isotherm, isohyet, contour — lines joining equal values of anything.
An italic capital I, treating the proton and neutron as one particle.
An element symbol with mass number above and atomic number below, to its left.
A raised mass number before an element symbol in a formula.
A stationary front line across the archipelago.
A dated line sweeping up the archipelago.
Degrees 5 and 6 each split into two.
A typhoon named by its number in the year.
Nested circles around a typhoon centre.
The station and front notation of the Japanese chart.
An empty circle.
A circle with a bar through it.
A circle with a small filled centre.
A circle filled with a hatched band.
A circle filled with a cross-hatch.
A broad banded arrow showing a fast upper-level current.
A ten-degree shaking scale written as shindo.
A short line marking a fracture with no displacement.
A capital J, the SI unit symbol for the joule.
A continuous count of days used in astronomy.
A stylised numeral four or Greek zeta crossed by a bar — Jupiter, and tin.
A chromosome complement in one line.
A capital K, the SI unit symbol for the kelvin.
A lower-case k, the SI prefix for a factor of one thousand.
The two-letter symbol kg, the SI unit symbol for the kilogram.
A graded mask-and-particle panel.
Stippling between two shorelines.
A turned h, for the French u sound in lui.
The letter w, used in phonetic transcription for a w sound.
A raised letter w marking lip rounding.
A hooked v, for a v-like sound without friction.
A letter v with a rightward hook at the top.
A letter m with a rightward tail on its last leg.
A small tapered vessel for strong heating.
A cone above a narrow stem.
A script capital L, kinetic energy minus potential energy.
The eleventh Greek letter, used for wavelength, eigenvalues and anonymous functions.
A circle with a cross inside it, marking a lamp or indicator.
A triangle or squared nabla, summing second derivatives.
A crescent opening to the right, marking the waning half moon.
A raised letter l marking release over the tongue sides.
A point group symbol with inversion added.
A diode symbol with two arrows pointing away, marking a light-emitting diode.
A pair of triangles marking a long sound.
An italic capital L, counting electrons, muons and taus.
An open-left hook beneath a letter, marking reduced rounding.
An angle bracket opening to the right, stating that the left value is smaller.
A less-than wedge with a bar beneath it, allowing equality as well.
A tube within a water jacket, drawn sloping.
A brick-like pattern marking a limestone unit.
An arrow marking a linear fabric and its plunge.
A seagull shape beneath a letter, marking tongue-to-lip contact.
A low curve joining two sounds without a break.
A capital or lower-case L, the symbol for the litre.
A pointed caret, denoting conjunction in formal logic.
A pointed V, denoting inclusive disjunction in formal logic.
Two dots showing electrons not used in bonding.
A Greek gamma, how much relativity changes things.
The letter D marking a comet no longer seen.
A vertical stem with a mark low on it, for a low pitch.
A tack pointing down beneath a letter, marking an opener sound.
The two letters lm, the SI unit symbol for the lumen.
A Roman numeral after a spectral type.
A Latin term with a proper name.
The two letters lx, the SI unit symbol for the lux.
A bold capital H, measured in amperes per metre.
A bold capital B, measured in tesla.
A bold capital A, a field whose curl is the magnetic field.
A double vertical bar marking a full prosodic break.
A circle with an arrow pointing up and right — Mars, the male sign, and iron.
The tallest peak set to one hundred.
Square or round brackets enclosing a grid of numbers, marking a matrix.
A tall graduated cylinder on a wide base.
A horned circle above a cross — Mercury, and quicksilver.
The italic word meso before a compound's name.
An M and a number naming a deep-sky object.
A coded aviation weather report in fixed abbreviated fields.
A constellation name in adjectival form.
A lower-case m, the SI unit symbol for the metre.
A lowercase g with two lower indices, defining distance itself.
A lower-case Greek mu with a straight descender, used as the SI prefix for one millionth.
A vertical stem with a mark at mid height, for a middle pitch.
Three figures in round brackets naming a plane.
A bar above a figure marking a negative index.
A date recording when work stopped.
A line where a seam meets the surface.
A hatched area of extracted ground.
A crossed circle marking a vertical shaft.
A marked point where a mineral has been found.
A single vertical bar marking a short prosodic break.
A name proposed by the discoverer and approved.
A number in parentheses before a name.
A year with two letters and a number.
The mathematical sign for subtraction, written as a single horizontal stroke.
A heavy solid line marking a mirror.
A number from one to ten ranking scratch resistance.
The three letters mol, the SI unit symbol for the mole.
An italic capital I or J, resistance to angular acceleration.
A p with a circumflex, standing for a derivative times minus i ℏ.
A bold or italic p, mass times velocity.
A fold trace marking a single step in level strata.
A crescent — the Moon, and silver in alchemy.
A ridged line marking glacially deposited debris.
An open-right hook beneath a letter, marking extra rounding.
Two karyotypes separated by an oblique.
A circle containing the letter M, marking an electric motor.
The twelfth Greek letter, and the SI prefix for one millionth.
Dashes without lamination marking a mudstone unit.
A letter and subscript naming a symmetry species.
The diagonal cross used to indicate multiplication.
An inverted solid triangle, denoting the vector differential operator.
A raised letter n marking release through the nose.
A tilde above a letter, marking nasal airflow.
An upsilon shape, for the vowel of English foot.
A small capital Y, for a lax front rounded vowel.
A small capital I, for the vowel of English kit.
A turned a, for a low central vowel.
An a-e ligature, for the vowel of English trap.
A horizontal bar with a short downward tick at its right end, denoting logical not.
A trident — Neptune.
The letters NGC with a number.
A circle with three bonds from the centre and three from the rim.
A capital N, the SI unit symbol for the newton.
A four-part diamond rating health, fire, reactivity and special hazards.
Letters naming a peak's splitting pattern.
A small corner mark showing an unreleased stop.
The letter C with a year and code.
A small arc beneath a letter, marking it as not a syllable.
A capital N with a mean and variance in brackets, naming a bell-shaped distribution.
An equals sign struck through by a diagonal stroke, meaning inequality.
An arrow with a Greek letter naming the decay mode.
A Greek mu with a capital N subscript, the nuclear magnetic unit.
A capital H with a subscript zero, naming the hypothesis being tested.
A capital N with a circumflex, counting quanta.
The letters NA, a lens's light-gathering cone.
A line carrying both triangles and semicircles, where a cold front has caught a warm one.
The horseshoe-shaped capital letter used to denote the ohm, the SI unit of electrical resistance — visually identical to, but formally distinct from, the Greek letter omega.
The last Greek letter, used for angular velocity — and the source of the ohm sign.
A turned script a, for the vowel of English lot.
A script a, for the vowel of English father.
A small capital O-E ligature, for a low front rounded vowel.
The letter a, for the vowel of French patte.
A hachured outline marking a surface working.
An open o, for the vowel of English thought.
A turned v, for the vowel of English strut.
A closed reversed epsilon, for a rounded central vowel.
A reversed epsilon, for the English nurse vowel.
An o-e ligature, for the vowel of French coeur.
An epsilon, for the vowel of English dress.
Two small circles joined by a straight line.
A plus or minus in brackets before a compound's name.
An anticline trace with both arrows pointing one way.
A dip symbol with a hooked tick, marking inverted strata.
Roman numerals in brackets naming an element's oxidation state.
A lower-case p followed by a probability, reporting how surprising a result would be.
The letter j, used in phonetic transcription for a y sound.
A turned y, for the Italian gli sound.
A letter n with a leftward tail, for the Spanish enye sound.
A raised letter j marking a y-like colouring.
A double-barred vertical stroke, for a palatal click.
A bracket showing the quadrant.
Two vertical strokes side by side, stating that two lines never meet.
A capital P, reflecting space through the origin.
A lowercase delta with a raised plus or minus.
A rounded d with a curled top, marking differentiation in one variable.
An italic capital Z, a weighted count of a system's states.
The two letters Pa, the SI unit symbol for the pascal.
A sigma with a subscript x, y or z, three two-by-two matrices.
Brackets around an individual's symbol.
The squares, circles and connecting lines of a formal family diagram.
A symbol carrying a letter for an ongoing pregnancy.
A square for a male individual, a circle for a female, a diamond where unknown.
A symbol with an abbreviation beneath.
Lines converging to a single point.
Tensors drawn as shapes with legs.
A percent sign with an extra circle, meaning 'per thousand'.
Two small circles either side of a diagonal stroke, meaning 'per hundred'.
A number, the letter P and a name.
A Greek mu with a nought subscript, the magnetic constant.
An upright T shape with the crossbar at the foot, stating that two lines meet at a right angle.
A shallow flat dish with an overlapping lid.
A raised reversed glottal stop marking throat constriction.
A Greek phi or delta, how far into a cycle a wave is.
Subscript letters saying whether a substance is solid, liquid, gas or dissolved.
The twenty-first Greek letter, used for the golden ratio and magnetic flux.
A circle within a square within a triangle within a circle — the emblem of the great work.
Branches that mean relatedness, not time.
The Greek letter used for the ratio of a circle's circumference to its diameter.
A lowercase p before a capital K with an a subscript.
An italic lower-case h, denoting the quantum of action.
A Latin descriptor with a themed name.
The mathematical sign for addition, written as an upright cross.
A plus sign above a minus stroke, giving a tolerance or two possible values.
Peaks labelled with plane indices.
A bold capital S, the direction and rate of energy flow.
A downward arrow after a formula, marking a solid falling out of solution.
Dots for rain, stars for snow, triangles for hail — and doubling means heavier.
A tiny line drawing of how pressure has moved over three hours.
Straight slanted ticks for feet, inches, minutes and seconds.
A capital P opening a space group symbol.
An arrow marking the individual the chart was drawn for.
A large capital pi, denoting the product of a sequence of terms.
A height measuring how far a summit rises above its saddle.
A Greek tau, the time a clock actually reads.
A looped form resembling an open alpha, stating a constant ratio.
An italic capital Q, how slowly an oscillator loses energy.
Six lowercase letters u, d, c, s, t and b.
Italic letters naming the handedness of a stereocentre.
A capital R giving agreement as a fraction.
The letters rac or a bracketed plus-minus sign.
A colour ramp showing how strongly rain reflects radar.
A three-bladed trefoil, conventionally black on a yellow background, warning of ionising radiation hazards.
A single dot marking an unpaired electron.
A date with an error, a laboratory code and a calibration marker.
Filled dots whose number and grouping give rain's intensity and continuity.
A tack pointing up beneath a letter, marking a closer sound.
An italic capital X, the imaginary part of impedance.
A single-headed arrow separating reactants from products.
Reagents above an arrow and conditions below it.
Isobars, fronts, pressure centres and station circles, in one picture.
A lowercase z, fractional stretching of a wavelength.
A struck-through h, Planck's constant divided by two pi.
A flask with a vertical condenser above it, in an apparatus diagram.
An italic n, how much a medium slows light.
A Greek rho, resistance scaled out of the shape.
A zigzag or a plain rectangle in a circuit, marking a resistor.
A double-headed straight arrow between two drawn structures.
A vertical rod on a heavy base with an adjustable clamp.
A minus sign beneath a letter, marking a backer articulation.
A turned r with a rightward tail.
A tap letter with a rightward tail, for a retroflex flap.
A letter l with a rightward tail.
A letter n with a rightward tail, for a retroflex n sound.
A double-shafted open arrow read backwards from the product.
A fault line marking an upthrown hanging wall.
The seventeenth Greek letter, used for density and resistivity.
A capital R marking a rhombohedral setting.
A small hook marking an r-coloured vowel.
A capital R with two indices, a contraction of the Riemann tensor.
A zigzag or marked line along an axis of high pressure.
A capital R with four indices, the full description of curvature.
A celestial coordinate measured in hours rather than degrees.
Repeating patterns standing for rock type in a section.
A rotation symbol with an open circle inside.
A spherical vessel with a narrow neck.
A capital R with an infinity subscript, the hydrogen spectrum scale.
A transparent barrier between operator and apparatus.
Two upright strokes, marking a junction whose potential is negligible.
A letter x with a horizontal bar above it, standing for the average of a sample.
An even scatter of dots marking a sandstone unit.
A crossed sickle shape — Saturn, and lead.
Wavy parallel lines marking a foliated metamorphic rock.
Symmetry named by a letter and a subscript.
An upside-down e, for the unstressed vowel of English about.
An r with a subscript s, the size of a black hole's horizon.
A rotation symbol carrying tails.
A lower-case s, the SI unit symbol for the second.
A lowered vertical stroke before a lightly stressed syllable.
A vertical slice, drawn to rule.
A shaded wave against two-way time.
A pear-shaped vessel with a tap at the base.
Letters stacked by information.
Braces enclosing a variable, a separator and a condition, defining a set by a rule.
Six short strokes radiating from a common centre.
Fine horizontal lines marking a shale unit.
A solid triangle beneath a precipitation mark.
A conical flask with a tube on its neck.
A capital A, B or C marking one centred face pair.
A clock keyed to the stars rather than to the sun.
The two letters Sv, the SI unit symbol for the sievert.
The eighteenth Greek letter, used for standard deviation and stress.
Greek letters naming how orbitals overlap in a bond.
How a number is written to state how well it is known.
A small hachured depression in soluble rock.
A point group symbol with dots for missing directions.
A filled hexagon marking a sixfold axis.
A zigzag of lines whose vertices are carbon atoms, with hydrogens left undrawn.
A circle shaded in eighths to show how much sky is cloudy.
A single line of letters, digits and brackets encoding a structure.
Six-pointed asterisks whose number gives the snowfall's intensity.
A letter marking a mineral topsoil.
A letter marking a subsoil of accumulation.
A letter marking little-altered parent material.
Capital letters naming layers down a soil profile.
A letter marking an organic layer.
A triangle plotting three particle fractions.
A capital K with sp as a subscript.
A lattice letter followed by symmetry elements.
An italic lower-case c, denoting the speed of light in vacuum.
Up and down arrows in boxes filling electron orbitals.
An outline with outward hachures marking waste ground.
An italic k, stiffness in newtons per metre.
A small circle with a tail, marking emerging groundwater.
A hooked stroke with a horizontal bar, indicating a root of a number.
A lower-case sigma, or a letter s, standing for the spread of a distribution.
A capital E with a nought superscript, in volts.
A small circle, often struck through, raised after a quantity.
A circle surrounded by numbers, each position meaning a fixed thing.
Triangles on one side, semicircles on the other, pointing opposite ways.
A Greek sigma, relating temperature to radiated power.
A number that runs backwards, smaller meaning brighter.
A capital letter with a digit subdivision.
An italic capital S, counting strange quarks with a sign flip.
A flat horizontal layer, the lowest and dullest cloud.
A long line with a short tick and a number, giving a bed's attitude.
A fault line with paired arrows showing lateral movement.
A closed trace with arrows pointing inward all round.
A closed trace with arrows pointing outward all round.
A capital F carrying three indices.
A rounded bracket opening right, stating that one set is contained in another.
The capital Greek sigma, used to indicate a sum over a series.
A circle with a dot at its centre — the Sun, and gold in alchemy.
The letters SN, a year and a letter code.
An italic capital B, the imaginary part of admittance.
A break in a wire bridged by a hinged line, marking a switch.
A vertical stroke beneath a letter, marking a syllable nucleus.
Five-figure groups encoding a whole observation for transmission.
Letters written above and below a symbol, marking a tensor's components.
A skewed thermodynamic diagram that tells a forecaster whether air will rise.
A superscript, a capital letter and a subscript together.
A capital T, the SI unit symbol for the tesla.
A narrow tube closed with a rounded end.
A mirrored capital E, the existential quantifier of formal logic.
Three dots in an upward-pointing triangle, introducing a conclusion.
An ellipsoid drawn for atomic displacement.
The eighth Greek letter, the default name for an angle.
A long tube with a bulbous flared top.
A filled triangle marking a threefold axis.
A capital R with a hooked tail and an arrowhead.
A single wave-shaped stroke marking equivalence, similarity or distribution.
Mixed angular and rounded clasts with no sorting.
A Z or a signed offset fixing a time to a zone.
Letters for the faces of a tooth.
A Greek tau, or a capital M in engineering.
Two coils facing each other across parallel lines, marking a transformer.
A boxed figure on a transport label.
A small square marking an exploratory excavation.
A three-legged stand with a mesh square on top.
A bold line with no triangles: a pressure feature without a front.
A matrix or plane naming a twin relation.
A filled lens shape marking a twofold axis.
Four digits, often on an orange plate.
A wavy line marking missing time in a rock sequence.
A rounded U shape, denoting everything in either of two sets.
One to thirty-two, straight through.
An upward arrow marking a raised pitch register.
A circle with a vertical stroke rising to a cross — Uranus.
A number from 1 upward, with colour bands and a threshold at 3.
A small capital N, for a nasal made at the uvula.
A small capital R, for a trill made at the uvula.
An epsilon with a zero subscript, in every electrostatic formula.
Letters assigned in an order almost nobody can guess.
The letters Var, or a squared sigma, measuring spread.
A short arrow written above a letter, marking it as a vector.
A turned m with a long right leg.
A small capital L, for a lateral made at the soft palate.
A letter n with a descending tail, for the ng sound.
A raised gamma marking a dark colouring.
A circle above a cross — Venus, the female sign, and copper.
A strike line with ticks both sides, marking upright strata.
A Greek letter numbering a normal mode.
The letter z, used in phonetic transcription for a z sound.
A letter d with a leftward hook at the top.
A lezh, for a voiced lateral fricative.
The letter d, used in phonetic transcription for a d sound.
A Greek beta, for a voiced sound made between the lips.
A letter b with a leftward hook at the top.
The letter b, used in phonetic transcription for a b sound.
An eth, a crossed d, for the th sound of English this.
A small wedge beneath a letter, marking it as voiced.
A hooked h, for a breathy h sound.
The letter v, used in phonetic transcription for a v sound.
A curled j, for a voiced sound made at the hard palate.
A dotless j with a crossbar and a hook.
A dotless j with a crossbar, for a voiced palatal stop.
A reversed glottal stop letter, for the Arabic ayin.
An ezh, for the s sound in English measure.
A letter z with a rightward tail, for a retroflex z.
A letter d with a rightward tail, for a retroflex d sound.
An inverted small capital R, for the French r.
A small capital G with a leftward hook.
A small capital G, for a voiced uvular stop.
A gamma-like letter, for a voiced sound at the soft palate.
A letter g with a leftward hook at the top.
A single-storey script g, for a hard g sound.
The letter s, used in phonetic transcription for an s sound.
A belted l, for the Welsh double-l sound.
The letter t, used in phonetic transcription for a t sound.
A Greek phi, for air forced between the lips.
The letter p, used in phonetic transcription for a p sound.
A Greek theta, for the th sound of English thin.
A small ring beneath a letter, marking it as voiceless.
The letter h, used in phonetic transcription for an h sound.
A turned w, for the wh sound of some English accents.
The letter f, used in phonetic transcription for an f sound.
A c with a cedilla, for the German ich sound.
The letter c, used in phonetic transcription for a palatal stop.
A crossed h, for a constricted sound in the throat.
A long s, for the sh sound of English ship.
A letter s with a rightward tail, for a retroflex s.
A letter t with a rightward tail, for a retroflex t sound.
A Greek chi, for a rasping sound at the uvula.
The letter q, used in phonetic transcription for a uvular stop.
The letter x, for the ch sound of Scottish loch.
The letter k, used in phonetic transcription for a k sound.
A number from zero to eight rating an eruption's size.
A small marked circle where lava reached the surface.
A capital V, the SI unit symbol for the volt.
A pear-shaped vessel with a single graduation line.
A tube with a central bulb and one graduation.
A capital W with a charge superscript, the charged weak carrier.
A line with solid semicircles along one side, marking advancing warm air.
A squeeze bottle with a bent delivery tube.
A shallow circular dish used as a cover or surface.
A capital W, the SI unit symbol for the watt.
A Greek psi standing for a quantum state's amplitude.
A Greek lambda, denoting the distance between successive wave peaks.
An italic k or a tilde-topped nu, waves per unit length.
A single wavy line, meaning the configuration is unspecified.
A solid triangle showing a bond coming towards the reader.
Two curves swapping order to flag a zone.
A vertical strip carrying one measurement.
An arrow showing wind direction on a public forecast map.
A shaft with feathers, giving wind direction and speed in one mark.
A multiplicity figure with a letter.
A capital Z with a nought superscript, the neutral weak carrier.
A lowercase z counting standard deviations from the mean.