decompression vs alleviation

decompression and alleviation both are nouns.

Word	Noun	Adjective	Verb	Adverb
decompression	Yes	No	No	No
alleviation	Yes	No	No	No

As nouns, alleviation is a hypernym of decompression; that is, alleviation is a word with a broader meaning than decompression:

decompression: relieving pressure (especially bringing a compressed person gradually back to atmospheric pressure)
alleviation: the act of reducing something unpleasant (as pain or annoyance)

Other hypernyms of decompression include easement, easing, relief.

decompression (noun)	alleviation (noun)
relieving pressure (especially bringing a compressed person gradually back to atmospheric pressure)	the act of reducing something unpleasant (as pain or annoyance)
restoring compressed information to its normal form for use or display	the feeling that comes when something burdensome is removed or reduced