light up vs illumine

light up and illumine both are verbs.

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

As verbs, light up and illumine are synonyms defined as:

Other synonyms of light up include illume, illuminate, light.

light up (verb)	illumine (verb)
introduce light into	introduce light into
begin to smoke
become clear
start to burn with a bright flame
ignite