decrease vs change of magnitude

decrease and change of magnitude both are nouns.

Word	Noun	Adjective	Verb	Adverb
decrease	Yes	No	Yes	No
change of magnitude	Yes	No	No	No

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

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

decrease (verb)	change of magnitude (verb)
decrease in size, extent, or range
make become smaller