Noun:
1: single, unity, i, 1, ace, one the smallest whole number or a numeral representing this number; "he has the one but will need a two and three to go with it"; "they had lunch at one"
2: one a single person or thing; "he is the best one"; "this is the one I ordered"
Adjective:
1: ane, cardinal, 1, one, i used of a single unit or thing; not two or more; "`ane' is Scottish"
2: united, one, unitary having the indivisible character of a unit; "a unitary action"; "spoke with one voice"
3: one, same of the same kind or quality; "two animals of one species"
4: one, extraordinary used informally as an intensifier; "that is one fine dog"
5: one, indefinite indefinite in time or position; "he will come one day"; "one place or another"
6: one, combined being a single entity made by combining separate components; "three chemicals combining into one solution"
7: one, incomparable, peerless, unrivalled, uncomparable, matchless, unmatchable, one and only, unrivaled, unmatched, nonpareil eminent beyond or above comparison; "matchless beauty"; "the team's nonpareil center fielder"; "she's one girl in a million"; "the one and only Muhammad Ali"; "a peerless scholar"; "infamy unmatched in the Western world"; "wrote with unmatchable clarity"; "unrivaled mastery of her art"