Definition of act:

part of speech: verb

To do; to exert power; to perform.

part of speech: noun

A deed; a doing; power exerted; an exploit; a decree or law.

Usage examples:

• Yes, he must act Payne Erskine in "The Eye of Dread".

• And this was the least of it, that in this act He became a public and marked character. Marcus Dods in "The Expositor's Bible: The Gospel of St. John, Vol. I".

• An act is strictly and originally something accomplished by an exercise of power, in which sense it is synonymous with deed or effect. Action is a doing. Act is therefore single, individual, momentary; action a complex of acts, or a process, state, or habit of exerting power. We say a virtuous act but rather a virtuous course of action. We speak of the action of an acid upon a metal, not of its act Act is used, also, for the simple exertion of power; as, an act of will. In this sense an act does not necessarily imply an external effect, while an action does. Morally, the act of murder is in the determination to kill; legally, the act is not complete without the striking of the fatal blow. Act and deed are both used for the thing done, but act refers to the power put forth, deed to the result accomplished; as, a voluntary act a bad deed. In connection with other words act is more usually qualified by the use of another noun, action by an adjective preceding; we may say a kind act though oftener an act of kindness, but only a kind action, not an action of kindness. As between act and deed, deed is commonly used of great, notable, and impressive acts, as are achievement, exploit, and feat. in "".

• He put his arm tenderly about the trembling little form, and the act brought the tears and he thought her softened. Payne Erskine in "The Eye of Dread".