Noun

• S: (n) one, 1, I, ace, single, unity (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"
• S: (n) one (a single person or thing) "he is the best one"; "this is the one I ordered"

Adjective

• S: (adj) one, 1, i, ane (used of a single unit or thing; not two or more) "`ane' is Scottish"
• S: (adj) one, unitary (having the indivisible character of a unit) "a unitary action"; "spoke with one voice"
• S: (adj) one (of the same kind or quality) "two animals of one species"
• S: (adj) one, right ((informal) very; used informally as an intensifier) "that is one fine dog"; "a right fine day"
• S: (adj) one (indefinite in time or position) "he will come one day"; "one place or another"
• S: (adj) one (being a single entity made by combining separate components) "three chemicals combining into one solution"
• S: (adj) matchless, nonpareil, one, one and only, peerless, unmatched, unmatchable, unrivaled, unrivalled (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"