infant vs kid

infant and kid both are nouns.

Word	Noun	Adjective	Verb	Adverb
infant	Yes	No	No	No
kid	Yes	No	Yes	No

As nouns, kid is a hypernym of infant; that is, kid is a word with a broader meaning than infant:

infant: a very young child (birth to 1 year) who has not yet begun to walk or talk
kid: a human offspring (son or daughter) of any age

Other hypernyms of infant include child.

infant (noun)	kid (noun)
a very young child (birth to 1 year) who has not yet begun to walk or talk	young goat
	a young person of either sex
	a human offspring (son or daughter) of any age
	soft smooth leather from the hide of a young goat

infant (verb)	kid (verb)
	be silly or tease one another
	tell false information to for fun