The same character recorded twice — once as a Greek letter, once as the quantity it most often denotes.
They are the same character, and that is the point. The catalogue records the letter itself and its use as a physical quantity separately, because a reader arriving from a physics equation wants wavelength and a reader arriving from an alphabet wants the letter. In physics the same λ is also the decay constant, and in linear algebra an eigenvalue.
The same character recorded twice: once as a Greek letter, once as the physical quantity it most often denotes.
Drawn from the visual attributes recorded for each symbol. Only traits the two records disagree about are listed.
| Trait | Lambda | Wavelength symbol |
|---|---|---|
| Built from | letter like, lines and dots | letter like |
| Lambda | Wavelength symbol | |
|---|---|---|
| What it is | The eleventh Greek letter | A quantity symbol using that letter |
| Chief meaning | A letter, used for many things | Wavelength |
| Other uses | Wavelength, decay constant, eigenvalue | Decay constant, eigenvalue |
| Code point | U+03BB | U+03BB — identical |
| Relationship (from Symbolwise's records) | Commonly confused with Wavelength symbol — The same character recorded twice: once as a Greek letter, once as the physical quantity it most often denotes. | Commonly confused with Lambda — The same character; the catalogue records the letter itself and this its use as a physical quantity. |
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for the widely-agreed uses of the letter across fields and for its history. Not used to assert that any one use is the letter's definitive meaning — no body defines that, and the record says so.
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol denotes in ordinary scientific practice and for which fields reuse it, never for a claim that any body assigns the letter its meaning.
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.