alleviation vs decrease

alleviation and decrease both are nouns.

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

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

alleviation: the act of reducing something unpleasant (as pain or annoyance)
decrease: the act of decreasing or reducing something

Other hypernyms of alleviation include diminution, reduction, step-down.

alleviation (noun)	decrease (noun)
the act of reducing something unpleasant (as pain or annoyance)	the act of decreasing or reducing something
the feeling that comes when something burdensome is removed or reduced	the amount by which something decreases
	a change downward
	a process of becoming smaller or shorter

alleviation (verb)	decrease (verb)
	decrease in size, extent, or range
	make become smaller