kindergartner vs nipper

kindergartner and nipper both are nouns.

Word	Noun	Adjective	Verb	Adverb
kindergartner	Yes	No	No	No
nipper	Yes	No	No	No

As nouns, nipper is a hypernym of kindergartner; that is, nipper is a word with a broader meaning than kindergartner:

Other hypernyms of kindergartner include child, fry, kid, minor, nestling, shaver, small fry, tiddler, tike, tyke, youngster.

kindergartner (noun)	nipper (noun)
a child who attends a preschool or kindergarten	a grasping structure on the limb of a crustacean or other arthropods
	a young person of either sex