(grammar) A noun which, though singular, refers to a group of things or animals. Examples: a school of fish, a pride of lions.

(psychology) The common experiences, thoughts and opinions of a large group of people taken as a whole.

The concept of maintaining peace among all nations or members of a group by making the security concerns of one member important to all members.

plural of collective noun

(US) To make a telephone call in which the cost of the call is paid by the person receiving the call.

(programming) To reclaim resources which are no longer in use; to run a garbage collector.

(Canada, US) A service, generally run by local government, for transporting household garbage to the appropriate facility.

Any organisation which manages or administers copyright or rights related to copyright as its sole purpose or as one of its main purposes

A collection of works of art housed together.

The hobby of collecting and displaying postage stamps and related items. / (figuratively, usually derogatory) Collection of items or information of no intrinsic value.