(uncountable) State of being one or undivided; unity. / (countable) The product of being one or undivided.

(chiefly Britain, Commonwealth of Nations except Canada, Ireland) Alternative form of no one

A specified object, thing or person (especially one nearby or known).

present participle of one

As the first in a number of examples or reasons. / As a single given example, often the most obvious or important one and almost certainly enough to sway the argument, of several reasons for something.

(collectible card games) A card included in a deck only once.

(often with with) In harmony or unity. / (often with with) In agreement, unanimous, of the same opinion. / (archaic) Into a state of harmony, friendship or reconciliation.

In a single attempt. / (theater) Performed downstage between the frontmost pieces of scenery.

(formal) simultaneously, at the same time, all together / (chiefly UK, formal) in agreement

(UK, dated, informal) To be amusing in a slightly challenging way.