execution vs mechanism

execution and mechanism both are nouns.

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

As nouns, mechanism is a hyponym of execution; that is, mechanism is a word with a more specific, narrower meaning than execution:

execution: the act of performing; of doing something successfully; using knowledge as distinguished from merely possessing it
mechanism: the technical aspects of doing something

Other hyponyms of execution include specific performance, linguistic performance, mechanics, officiation.

execution (noun)	mechanism (noun)
putting a condemned person to death	the technical aspects of doing something
unlawful premeditated killing of a human being by a human being	device consisting of a piece of machinery; has moving parts that perform some function
the act of performing; of doing something successfully; using knowledge as distinguished from merely possessing it	(philosophy) the philosophical theory that all phenomena can be explained in terms of physical or biological causes
the act of accomplishing some aim or executing some order	a natural object resembling a machine in structure or function
a routine court order that attempts to enforce the judgment that has been granted to a plaintiff by authorizing a sheriff to carry it out	the atomic process that occurs during a chemical reaction
(law) the completion of a legal instrument (such as a contract or deed) by signing it (and perhaps sealing and delivering it) so that it becomes legally binding and enforceable
(computer science) the process of carrying out an instruction by a computer