shorten vs curtail

shorten and curtail both are verbs.

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

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

shorten: make shorter than originally intended; reduce or retrench in length or duration
curtail: terminate or abbreviate before its intended or proper end or its full extent

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

shorten (verb)	curtail (verb)
become short or shorter	place restrictions on
make shorter than originally intended; reduce or retrench in length or duration	terminate or abbreviate before its intended or proper end or its full extent
reduce in scope while retaining essential elements
edit by omitting or modifying parts considered indelicate
make short or shorter