ACT (Lat. actus, actum), something done, primarily a voluntary deed or performance, though any accomplished fact is often included. The signification of the word varies according to the sense in which it is employed. It is often synonymous with “statute” (see Act of Parliament). It may also refer to the result of the vote or deliberation of any legislature, the decision of a court of justice or magistrate, in which sense records, decrees, sentences, reports, certificates, &c., are called acts.

In law it means any instrument in writing, for declaring or justifying the truth of a bargain or transaction, as: “I deliver this as my act and deed.” The origin of the legal use of the word “act” is in the acta of the Roman magistrates or people, of their courts of law, or of the senate, meaning (1) what was done before the magistrates, the people or the senate; (2) the records of such public proceedings.

In connexion with other words “act” is employed in many phrases, e.g. act of God, any event, such as the sudden, violent or overwhelming occurrence of natural forces, which cannot be foreseen or provided against. This is a good defence to a suit for non-performance of a contract. Act of honour denotes the acceptance by a third party of a protested bill of exchange for the honour of any party thereto. Act of grace denotes the granting of some special privilege.

In universities, the presenting and publicly maintaining a thesis by a candidate for a degree, to show his proficiency, is an act. “The Act” at Oxford, up to 1856 when it was abolished, was the ceremony held early in July for this purpose, and the expressions “Act Sunday,” “Act Term” still survive.

In dramatic literature, act signifies one of those parts into which a play is divided to mark the change of time or place, and to give a respite to the actors and to the audience. In Greek plays there are no separate acts, the unities being strictly observed, and the action being continuous from beginning to end. If the principal actors left the stage the chorus took up the argument, and contributed an integral part of the play, though chiefly in the form of comment upon the action. When necessary, another drama, which is etymologically the same as an act, carried on the history to a later time or in a different place, and thus we have the Greek trilogies or groups of three dramas, in which the same characters reappear. The Roman poets first adopted the division into acts, and suspended the stage business in the intervals between them. Their number was usually five, and the rule was at last laid down by Horace in the Ars Poetica

Neve minor, neu sit quinto productior actu
Fabula, quae posci vult, et spectata reponi.
If you would have your play deserve success,
Give it five acts complete, nor more nor less.” (Francis.)

On the revival of letters this rule was almost universally observed by dramatists, and that there is an inherent convenience and fitness in the number five is evident from the fact that Shakespeare, who refused to be trammelled by merely arbitrary rules, adopts it in all his plays. Some critics have laid down rules as to the part each act should sustain in the development of the plot, but these are not essential, and are by no means universally recognized. In comedy the rule as to the number of acts has not been so strictly adhered to as in tragedy, a division into two acts or three acts being quite usual since the time of Molière, who first introduced it. It may be well to mention here Milton’s Samson Agonistes as a specimen in English literature of a dramatic work founded on a purely Greek model, in which, consequently, there is no division into acts.

For “acting,” as the art and theory of dramatic representation (or histrionics, from Lat. histrio, an actor), see the article Drama.