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A letter and an operator that look nearly the same, distinguished by whether the right-hand stroke closes.
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 proportionality sign is drawn like an alpha whose right-hand stroke has been opened out, and the two are separate characters that a reader can easily take for one.
Drawn from the visual attributes recorded for each symbol. Only traits the two records disagree about are listed.
| Trait | Alpha | Proportional-to sign |
|---|---|---|
| Built from | letter like and abstract | abstract and letter like |
| Alpha | Proportional-to sign | |
|---|---|---|
| What it is | A letter naming a quantity | An operator relating two quantities |
| Where it sits | In place of a value | Between two values |
| Code point | U+03B1 GREEK SMALL LETTER ALPHA | U+221D PROPORTIONAL TO |
| Shape | A loop closing into a descending tail | A loop running out into an open curve |
| Relationship (from Symbolwise's records) | Commonly confused with Proportional-to sign — The proportionality sign is drawn like an alpha whose right-hand stroke has been opened out, and the two are separate characters that a reader can easily take for one. | Commonly confused with Alpha — The proportionality sign is drawn like an alpha with its right stroke opened out. |
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.
Unicode Code Chart: Mathematical Operators (U+2200–U+22FF)
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.
Glossary of mathematical symbols
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the notation means in ordinary mathematical practice and for attribution of its introduction, not for a claim that any body defines it.
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.
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.
Count what is around the centre. Three solid blades radiating from a small disc is ionising radiation; three broken rings overlapping a central circle is biological hazard. They are the same size, the same colours and the same three-fold arrangement, which is why signage catalogues themselves get them wrong — and the responses could not be less alike. One calls for distance, shielding and time; the other for containment, disinfection and a disposal route.