shorten vs truncate

shorten is not an adjective while truncate is an adjective.

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

As verbs, truncate is a hyponym of shorten; that is, truncate is a word with a more specific, narrower meaning than shorten:

shorten: make shorter than originally intended; reduce or retrench in length or duration
truncate: make shorter as if by cutting off

Other hyponyms of shorten include foreshorten, clip, curtail, cut short, syncopate, cut short.

shorten (adjective)	truncate (adjective)
	terminating abruptly by having or as if having an end or point cut off

shorten (verb)	truncate (verb)
become short or shorter	make shorter as if by cutting off
make shorter than originally intended; reduce or retrench in length or duration	approximate by ignoring all terms beyond a chosen one
reduce in scope while retaining essential elements	replace a corner by a plane
edit by omitting or modifying parts considered indelicate
make short or shorter