lighten up vs illumine

lighten up and illumine both are verbs.

Word	Noun	Adjective	Verb	Adverb
lighten up	No	No	Yes	No
illumine	No	No	Yes	No

As verbs, illumine is a hyponym of lighten up; that is, illumine is a word with a more specific, narrower meaning than lighten up:

Other hyponyms of lighten up include irradiate, illume, illuminate, light, light up.

lighten up (verb)	illumine (verb)
make more cheerful through the use of color	introduce light into
become lighter
become more cheerful
make more cheerful