one

1 being the one or ones of a class with no other members that's the one author I would stand in line for hours to get an autograph from Synonyms alone, lone, only, one-off, singular, sole, solitary, special, sui generis, uniqueRelated Words single, solo, unaccompanied, unattended; incomparable, inimitable, matchless, peerless, unequaled (or unequalled), unmatched, unparalleled, unrivaled (or unrivalled), unsurpassable, unsurpassed; distinct, distinctive, individual, separate; nonceNear Antonyms divers, manifold, multifarious, myriad; assorted, heterogenous, miscellaneous, mixed, motley, patchwork, promiscuous, varied; popular, prevailing, prevalent, rampant; perennial, recurrent, repeated

2 known but not named one person that I know said that it was the best movie he had ever seen Synonyms anonymous, given, certain, some, unidentified, unnamed, unspecifiedRelated Words particular, specificNear Antonyms known, named, specified

a U.S. currency bill representing 100 cents I don't have any ones on me just now Synonyms bone [slang], buck, clam, dollar, smacker [slang]Related Words greenback; dead presidents [slang]