bat boy vs assistant

bat boy and assistant both are nouns.

Word	Noun	Adjective	Verb	Adverb
bat boy	Yes	No	No	No
assistant	Yes	Yes	No	No

As nouns, assistant is a hypernym of bat boy; that is, assistant is a word with a broader meaning than bat boy:

bat boy: (baseball) a boy who takes care of bats and other baseball equipment
assistant: a person who contributes to the fulfillment of a need or furtherance of an effort or purpose

Other hypernyms of bat boy include help, helper, supporter, boy, male child.

bat boy (noun)	assistant (noun)
(baseball) a boy who takes care of bats and other baseball equipment	a person who contributes to the fulfillment of a need or furtherance of an effort or purpose

bat boy (adjective)	assistant (adjective)
	of or relating to a person who is subordinate to another