The Greek letter "alpha" (Α, α) is the first letter of the Greek alphabet and is used as a numeral to represent the numbers 1 and 1000. As a prefix, it can have different meanings: it can negate a word (e.g., "unknown" or "unjust"), indicate connection or fellowship (e.g., "simple" or "brother"), or sometimes add emphasis to a word. These uses depend on the context and specific word formation.