Pronunciation: (wun),[key] —adj. 1. being or amounting to a single unit or individual or entire thing, item, or object rather than two or more; a single: one woman; one nation; one piece of cake. 2. being a person, thing, or individual instance or member of a number, kind, group, or category indicated: one member of the party. 3. existing, acting, or considered as a single unit, entity, or individual.
4. of the same or having a single kind, nature, or condition: We belong to one team; We are of one resolve. 5. noting some indefinite day or time in the future: You will see him one day. 6. a certain (often used in naming a person otherwise unknown or undescribed): One John Smith was chosen. 7. being a particular, unique, or only individual, item, or unit: I'm looking for the one adviser I can trust. 8. noting some indefinite day or time in the past: We all had dinner together one evening last week. 9. of no consequence as to the character, outcome, etc.; the same: It's all one to me whether they go or not.
—n. 1. the first and lowest whole number, being a cardinal number; unity.
2. a symbol of this number, as 1 or I.
3. a single person or thing: If only problems would come one at a time! 4. a die face or a domino face having one pip.
5. a one-dollar bill: to change a five-dollar bill for five ones. 6. (cap.) Neoplatonism.the ultimate reality, seen as a central source of being by whose emanations all entities, spiritual and corporeal, have their existence, the corporeal ones containing the fewest of the emanations.
7. at one, a. in a state of agreement; of one opinion.
b. united in thought or feeling; attuned: He felt at one with his Creator. 8. one and all, everyone: They came, one and all, to welcome him home. 9. one by one, singly and successively: One by one the children married and moved away. 10. one for the road. See road (def. 8).
—pron. 1. a person or thing of a number or kind indicated or understood: one of the Elizabethan poets. 2. (in certain pronominal combinations) a person unless definitely specified otherwise: every one. 3. (with a defining clause or other qualifying words) a person or a personified being or agency: the evil one; the one I love. 4. any person indefinitely; anyone: as good as one would desire. 5. Chiefly Brit.(used as a substitute for the pronoun I): Mother had been ailing for many months, and one should have realized it. 6. a person of the speaker's kind; such as the speaker himself or herself: to press one's own claims. 7. something or someone of the kind just mentioned: The portraits are fine ones. Your teachers this semester seem to be good ones. 8. something available or referred to, esp. in the immediate area: Here, take one—they're delicious. The bar is open, so have one on me!
a suffix used in the names of ketones and analogous chemical compounds: lactone; quinone.