Act or ACT may refer to:
An actor (often actress for females; see terminology) is a person who portrays a character in a performance.
Active Directory (AD) is a directory service that Microsoft developed for Windows domain networks. It is included in most Windows Server operating systems as a set of processes and services.
In physiology, an action potential occurs when the membrane potential of a specific axon location rapidly rises and falls: this depolarisation then causes adjacent locations to similarly depolarise.
Activated carbon, also called activated charcoal, is a form of carbon processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions.
Action film is a film genre in which the protagonist or protagonists end up in a series of challenges that typically include violence, extended fighting, physical feats, and frantic chases.
Activision Publishing, Inc., also known as Activision, is an American video game publisher. It was founded on October 1, 1979 and was the world's first independent developer and distributor of video games for gaming consoles.