one

cardinal number

1》 the lowest cardinal number; half of two; 1. (Roman numeral: i or I.)

2》 a single person or thing.

    ↘single; sole.

    ↘denoting a particular item of a pair or number of items.

    ↘(before a person's name) a certain.

3》 identical; the same.

4》 informal a joke or story.

5》 informal, chiefly N. Amer. a noteworthy example of: he was one smart-mouthed troublemaker.

pronoun

1》 referring to a person or thing previously mentioned or easily identified.

2》 a person of a specified kind.

3》 [third person singular] used to refer to the speaker, or any person, as representing people in general.

Phrases

at one in agreement or harmony.

be one up on informal have an advantage over (someone).

one after another (or the other) following one another in quick succession.

one and all everyone.

one and only unique; single.

one another each other.

one by one separately and in succession.

one day at a particular but unspecified time in the past or future.

one or two informal a few.

Derivatives

onefold adjective

Origin

OE ān, of Gmc origin.

Usage

In modern English one as a pronoun meaning ‘anyone’ or ‘me and people in general’, as in one must try one's best, is generally only used in formal and written contexts, and can be regarded as pompous or over-formal. In informal and spoken contexts the normal alternative is you, as in you have to do what you can, don't you?