An act (from Latin 'acta', 'actum', act, action) is an action, the process of doing something.

It is also a written document that attests the legality of a transaction. In this sense there were found very ancient acts from the Babylonian period, carved on clay tablets in cuneiform writing.

An act also attests the legality of a pact or the peace after an armed conflict or war.

An act is one of the parts in which is divided a play or opera.

It is also called act the contemporary history, duly authorised, of the life and actions of a martyr.

An act (often Act) is a document or ordinance redacted by a king, president or legislative body to regulate on some subject. See Act of Parliament.