ac·tion

– noun
1. the process or state of acting or of being active
2. something done or performed; act; deed.
3. an act that one consciously wills and that may be characterized by physical or mental activity
4. habitual or usual acts; conduct.
5. energetic activity.
6. an exertion of power or force.
7. effect or influence.
8. way or manner of moving.
9. the mechanism by which something is operated, as that of a gun or a piano.
10. a military encounter or engagement; battle, skirmish, or the like.
11. actual engagement in fighting an enemy.
12. the main subject or story, as distinguished from an incidental episode.
13. an event or series of events that form part of a dramatic plot.
14. the gestures or deportment of an actor or speaker.
15. the appearance of animation, movement, or emotion given to figures by their attitude, position, or expression.

re·ac·tion

– noun
1. a reverse movement or tendency; an action in a reverse direction or manner.
2. action in response to some influence, event, etc.
3. action in response to a stimulus, as of the system or of a nerve, muscle, etc.