【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
  —Shirley

【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
  —Shak.
• what, are my deeds forgot?
  —Shak.
• little, nameless, unremembered acts of kindness and of love
  —Wordsworth

【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.