- It is an act of kindness/a kind act to help a blind man across the street.
- The attack on the ship was viewed as an act of war.
- The thief was apprehended (by the police) in the act of stealing a car.
- The act of straightening or extending a limb.
- This dreadful murder is surely the act of a madman.
- Such an act of cowardice by an officer shames his whole regiment.