Action means doing something: physically moving, working, or making something happen. When your teacher asks everyone to take action on cleaning up the classroom, she wants people to actually start picking things up and get the job done.

The word captures the difference between planning and doing. You might make elaborate plans for building a treehouse, but until you grab a hammer and some wood, there's no action. A character in a story who is a “person of action” doesn't hesitate or overthink: when something needs doing, they do it.

Action also describes exciting parts of movies or books where things happen: chase scenes, battles, or dramatic moments. Action movies feature car chases and fight choreography. When a film director shouts “Action!” she's signaling the actors to start performing.

In science, action often pairs with reaction: every action creates an equal and opposite reaction, meaning when you push against something, it pushes back with equal force. You can also take legal action (filing a lawsuit) or disciplinary action (consequences for breaking rules). The key idea connects them all: something is happening, not just being considered or discussed.