subtraction vs decrease

subtraction and decrease both are nouns.

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

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

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

subtraction (noun)	decrease (noun)
the act of subtracting (removing a part from the whole)	the act of decreasing or reducing something
an arithmetic operation in which the difference between two numbers is calculated	the amount by which something decreases
	a change downward
	a process of becoming smaller or shorter

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