General:
* Action: A general term for something done.
* Deed: A specific act, often with moral implications.
* Performance: A series of actions, especially in a theatrical context.
* Behavior: The way someone acts or behaves.
In a theatrical context:
* Scene: A part of a play.
* Part: A role in a play.
* Play: A theatrical performance.
In a legal context:
* Crime: An illegal act.
* Offense: A violation of a law or rule.
Other:
* Do: A general term for performing an action.
* Perform: To carry out an action, often in a skilled or artistic way.
* Execute: To carry out a plan or action.
To choose the best synonym, consider the specific meaning of "act" in the context you're using it.