skylark vs lark

skylark and lark both are nouns.

Word	Noun	Adjective	Verb	Adverb
skylark	Yes	No	Yes	No
lark	Yes	No	Yes	No

As nouns, lark is a hypernym of skylark; that is, lark is a word with a broader meaning than skylark:

skylark: brown-speckled European lark noted for singing while hovering at a great height
lark: any of numerous predominantly Old World birds noted for their singing

As verbs, skylark and lark are synonyms defined as:

Other synonyms of skylark include cavort, disport, frisk, frolic, gambol, lark about, rollick, romp, run around, sport.

skylark (noun)	lark (noun)
brown-speckled European lark noted for singing while hovering at a great height	any carefree episode
	any of numerous predominantly Old World birds noted for their singing
	a songbird that lives mainly on the ground in open country; has streaky brown plumage
	North American songbirds having a yellow breast

skylark (verb)	lark (verb)
play boisterously	play boisterously