The number represented by the Arabic numeral 1; the numerical value equal to that cardinal number. / (number theory) The first positive number in the set of natural numbers.

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

The digit or figure 1. / (mathematics) The neutral element with respect to multiplication in a ring. / (US) A one-dollar bill. / One o'clock, either a.m. or p.m.

Of a period of time, being particular. / Being a single, unspecified thing; a; any. / Sole, only. / Whole, entire. / In agreement. / The same. / Being a preeminent example.

To cause to become one; to gather into a single whole; to unite.

Matching each member of one set with exactly one member of another set. / (chiefly UK) Involving direct communication between two people.

A personal relationship between two people.

Individually in succession; one at a time.

(chiefly Canada, US) Involving direct communication or competition between two people. / (sports) Involving one attacker and one defender. / (mathematics) bijective or injective

A contest involving only one player on each side, especially of an activity often involving teams.