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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.
Look for the horizontal line. Fire is a plain upward triangle; air is the same triangle with a bar drawn across its upper part. Dropping the bar is the commonest error in reproductions of the element set, and it turns air into fire.
The same rule as fire and air, inverted. Water is a plain downward triangle; earth is the same triangle with a bar across its lower part. The four element signs are one designed set: two point up, two point down, and within each pair the bar is the only difference.
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.