Action, act and deed agree in designating something done or effected.
Action refers primarily to the process of acting; act and deed to the result, the thing done.
An action is usually regarded as occupying some time and involving more than one step; an act is more frequently thought of as momentary or instantaneous and as individual.
- the rescue of a shipwrecked crew is a heroic action; the launching of the lifeboat, a brave act
- a course of action
- the springs of action
- an act of vengeance
- caught in the act
In the plural action has frequently an ethical connotation and is loosely synonymous with conduct.
- by him [the Lord] actions are weighed
—I Sam 2:3
- only the actions of the just smell sweet and blossom in their dust
Deed refers to a thing as done; it invariably presupposes intelligence and responsibility in the agent and therefore often connotes, as act does not, illustriousness or achievement
- the deed is worthy doing
- what, are my deeds forgot?
- little, nameless, unremembered acts of kindness and of love
Deed is frequently opposed to word, as act to thought
- take the word for the deed
- I’ll endeavour deeds to match these words—Shak.
- be great in act, as you have been in thought—Shak.