—adj.
1 single and integral in number.
2 (with a noun implied) a single person or thing of the kind expressed or implied (one of the best; a nasty one).
3 a particular but undefined, esp. as contrasted with another (that is one view; one thing after another). b colloq. (as an emphatic) a noteworthy example of (that is one difficult question).
4 only such (the one man who can do it).
5 forming a unity (one and undivided).
6 identical; the same (of one opinion).
—n.
1 a the lowest cardinal number. b a thing numbered with it.
2 unity; a unit (one is half of two; came in ones and twos).
3 a single thing or person or example (often referring to a noun previously expressed or implied: the big dog and the small one).
4 colloq. an alcoholic drink (have a quick one; have one on me).
5 a story or joke (the one about the frog).
—pron.
1 a person of a specified kind (loved ones; like one possessed).
2 any person, as representing people in general (one is bound to lose in the end).
3 I, me (one would like to help).
Usage:
Often regarded as an affectation.
Phrases and idioms:
all one (often foll. by to) a matter of indifference. at one in agreement. for one being one, even if the only one (I for one do not believe it). for one thing as a single consideration, ignoring others. one another each the other or others (as a formula of reciprocity: love one another). one-armed bandit colloq. a fruit machine worked by a long handle at the side. one by one singly, successively. one day
1 on an unspecified day.
2 at some unspecified future date.
one-horse
1 using a single horse.
2 colloq. small, poorly equipped. one-liner colloq. a single brief sentence, often witty or apposite. one-man involving, done, or operated by only one man.
one-night stand
1 a single performance of a play etc. in a place.
2 colloq. a sexual liaison lasting only one night. one-off colloq. made or done as the only one; not repeated. one or two see OR(1). one-piece (of a bathing-suit etc.) made as a single garment.
one-sided
1 favouring one side in a dispute; unfair, partial.
2 having or occurring on one side only.
3 larger or more developed on one side. one-sidedly in a one-sided manner. one-sidedness the act or state of being one-sided. one-time former. one-to-one with one member of one group corresponding to one of another. one-track mind a mind preoccupied with one subject.
one-two colloq.
1 Boxing the delivery of two punches in quick succession.
2 Football etc. a series of reciprocal passes between two advancing players. one-up colloq. having a particular advantage. one-upmanship colloq. the art of maintaining a psychological advantage. one-way allowing movement or travel in one direction only.
Etymology: OE an f. Gmc
Useful english dictionary. 2012.