Dictionary

The digit or figure 1.

The neutral element with respect to multiplication in a ring.

A one-dollar bill.

One run scored by hitting the ball and running between the wickets; a single.

(impersonal pronoun, indefinite) One thing (among a group of others); one member of a group.

Example: Any one of the boys.  The big one looks good.  I want the green one.  A good driver is one who drives carefully.

(impersonal pronoun, sometimes with "the") The first mentioned of two things or people, as opposed to the other.

Example: She offered him an apple and an orange; he took one and left the other.

(indefinite personal pronoun) Any person (applying to people in general).

Example: One’s guilt may trouble one, but it is best not to let oneself be troubled by things which cannot be changed.  One shouldn’t be too quick to judge.

(pronoun) Any person, entity or thing.

Example: "driver", noun: one who drives.

Belonging to one.

A senior or first team (as opposed to a reserves team).

The cells located on the ground floor.