decrease vs modify

decrease is a noun but modify is not a noun.

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

As verbs, modify is a hypernym of decrease; that is, modify is a word with a broader meaning than decrease:

Other hypernyms of decrease include alter, change.

decrease (noun)	modify (noun)
the act of decreasing or reducing something
the amount by which something decreases
a change downward
a process of becoming smaller or shorter

decrease (verb)	modify (verb)
decrease in size, extent, or range	make less severe or harsh or extreme
make become smaller	add a modifier to a constituent
	cause to change; make different; cause a transformation