Two different characters that render almost identically, and which one you typed matters for search and sorting.
They look the same and are not the same. The micro sign is U+00B5 and is the SI prefix meaning one millionth; the Greek small letter mu is U+03BC and is a letter used for a coefficient of friction, a population mean, and much else. Text search, sorting and string comparison treat them as different characters, which is why a document can appear to contain a term it cannot find.
The micro sign and the Greek letter mu are different characters that render almost identically.
| Micro sign | Mu | |
|---|---|---|
| Code point | U+00B5 MICRO SIGN | U+03BC GREEK SMALL LETTER MU |
| What it means | The SI prefix micro, one millionth | A Greek letter used as a variable name |
| Where it belongs | Before a unit symbol: µm, µF, µSv | In an equation, as a quantity |
| Common substitution | A plain letter u where µ cannot be typed | Frequently typed in place of the micro sign |
| Relationship (from Symbolwise's records) | Commonly confused with Mu — The micro sign and the Greek letter mu are different characters that render almost identically. | Commonly confused with Micro sign — The SI prefix micro has its own character, U+00B5, separate from this Greek letter at U+03BC. They render almost identically and are substituted for each other constantly. |
Unicode Code Chart: Latin-1 Supplement (U+0080–U+00FF)
The Unicode Consortium · retrieved 2026-07-30
Authoritative for the character's code point, name and block only. Unicode assigns identity; it does not define what a symbol means in use.
Unicode Code Chart: Greek and Coptic (U+0370–U+03FF)
The Unicode Consortium · retrieved 2026-07-30
Authoritative for the character's code point, name and block only. Unicode assigns identity; it does not define what a symbol means in use.
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for origin narrative and for units the SI does not define, never for an official-definition claim.
Alpha is a Greek letter and stands for a quantity — an angle, a coefficient, a significance level. The proportionality sign is an operator and stands between two quantities to say they keep a constant ratio. The drawings differ in that the proportionality sign's right-hand stroke runs out in an open curve rather than closing into the letter's tail.
The becquerel counts nuclear decays — one per second — and says nothing about harm. The sievert weights absorbed energy by the kind of radiation delivering it, and so estimates biological effect. A becquerel of one isotope and a becquerel of another can carry very different risk, which is exactly why exposure limits and medical doses are stated in sieverts and never in becquerels.
Look at what follows. A prefix never stands alone — it is glued to a unit symbol, as in kW or kg. A constant stands by itself in an equation. Careful physical writing subscripts the constant as k_B for exactly this reason, and the kelvin's capital K is a third claimant to the same letter.
Equal-length lines mean a capacitor. Alternating long and short lines mean a battery, with the long line positive. If the second line is curved rather than straight it is a polarised capacitor — still a capacitor, but one that must be fitted the right way round.