one
(as an adjective) ‘being but a single unit or individual; being a single person, thing, etc. of the class mentioned’
(as a pronoun) ‘a single person or thing, an individual, somebody’
(as a noun) ‘the first or lowest of the cardinal numerals; single in kind, the same; the first whole number, consisting of a single unit; unity; the symbol representing one or unity’
Lexical development traced from the Tamil root:
E. on, oen, owne, un < O.E. an (adjective, pronoun, noun) ‘one’ < Proto-G. ainaz < uhn < oi-no- < Tamil oṉṟu