shorten vs decrease

shorten is not a noun while decrease is a noun.

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

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

Other hypernyms of shorten include diminish, fall, lessen.

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

Other hypernyms of shorten include lessen, minify.

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

shorten (verb)	decrease (verb)
become short or shorter	decrease in size, extent, or range
make shorter than originally intended; reduce or retrench in length or duration	make become smaller
reduce in scope while retaining essential elements
edit by omitting or modifying parts considered indelicate
make short or shorter