cheer vs lighten up

cheer is a noun but lighten up is not a noun.

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

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

Other hyponyms of cheer include exuberate, exult, jubilate, rejoice, triumph, buoy up, lighten.

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

Other hyponyms of cheer include buoy up, lighten.

cheer (noun)	lighten up (noun)
the quality of being cheerful and dispelling gloom
a cry or shout of approval

cheer (verb)	lighten up (verb)
become cheerful	make more cheerful through the use of color
spur on or encourage especially by cheers and shouts	become lighter
show approval or good wishes by shouting	become more cheerful
cause (somebody) to feel happier or more cheerful	make more cheerful
give encouragement to