The first Greek letter, used across science for angles, rates and particles.
Also known as: Greek letter alpha, Alpha symbol, α
Alpha is the first letter of the Greek alphabet and one of the most heavily reused symbols in science. Being first, it is the default choice whenever a field needs its first named quantity — which is why it means so many unrelated things.
Is a letter of the Greek alphabet before it is a symbol: what it denotes is fixed by the field it appears in, not by the character itself. The uses below are the documented conventions, not competing definitions.
Contexts: Mathematics
In physics, denotes an alpha particle — a helium nucleus emitted in radioactive decay.
Contexts: Mathematics
In statistics, denotes the significance level of a hypothesis test, commonly 0.05.
Contexts: Mathematics
In geometry and trigonometry, denotes an angle, usually the first one labelled.
Contexts: Mathematics
In finance, denotes a return in excess of a benchmark.
Contexts: Mathematics
In physics, denotes the fine-structure constant, written as a lowercase alpha.
Contexts: Mathematics
Carries its many meanings precisely because it is first: a field needing a name for its first quantity reaches for alpha, so the letter accumulates uses that have nothing to do with each other.
Contexts: Mathematics
Is used outside technical fields to mean 'first' or 'dominant', including in a widely repeated claim about wolf pack hierarchy that the researcher who popularised it has since retracted.
Recorded because readers meet the usage, not because it is sound. The original wolf study was of captive unrelated animals and its author has publicly disavowed the conclusion.
Contexts: Mathematics
A rounded loop on the left joined to a rising stroke that curves down to the right, like a lowercase a written in one continuous line.
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.