occlusion vs embolism

occlusion and embolism both are nouns.

Word	Noun	Adjective	Verb	Adverb
occlusion	Yes	No	No	No
embolism	Yes	No	No	No

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

occlusion: closure or blockage (as of a blood vessel)
embolism: occlusion of a blood vessel by an embolus (a loose clot or air bubble or other particle)

Other hyponyms of occlusion include laryngospasm, thromboembolism, thrombosis, coronary occlusion.

occlusion (noun)	embolism (noun)
the act of blocking	occlusion of a blood vessel by an embolus (a loose clot or air bubble or other particle)
an obstruction in a pipe or tube	an insertion into a calendar
(dentistry) the normal spatial relation of the teeth when the jaws are closed
(meteorology) a composite front when colder air surrounds a mass of warm air and forces it aloft
closure or blockage (as of a blood vessel)