action vs action mechanism

action and action mechanism both are nouns.

Word	Noun	Adjective	Verb	Adverb
action	Yes	No	Yes	No
action mechanism	Yes	No	No	No

As nouns, action and action mechanism are synonyms defined as:

action and action mechanism: the operating part that transmits power to a mechanism

As nouns, action mechanism is a hypernym of action; that is, action mechanism is a word with a broader meaning than action:

action: In firearms terminology, the mechanism that handles the ammunition (loads, locks, fires, and extracts the cartridges).
action mechanism: the operating part that transmits power to a mechanism

Other hypernyms of action include action.

action (noun)	action mechanism (noun)
the most important or interesting work or activity in a specific area or field	the operating part that transmits power to a mechanism
a judicial proceeding brought by one party against another; one party prosecutes another for a wrong done or for protection of a right or for prevention of a wrong
something done (usually as opposed to something said)
a military engagement
an act by a government body or supranational organization
the operating part that transmits power to a mechanism
In firearms terminology, the mechanism that handles the ammunition (loads, locks, fires, and extracts the cartridges).
the trait of being active and energetic and forceful
the series of events that form a plot
a process existing in or produced by nature (rather than by the intent of human beings)
the state of being active

action (verb)	action mechanism (verb)
put in effect
institute legal proceedings against; file a suit against