dayboy vs day boarder

dayboy and day boarder both are nouns.

Word	Noun	Adjective	Verb	Adverb
dayboy	Yes	No	No	No
day boarder	Yes	No	No	No

As nouns, day boarder is a hypernym of dayboy; that is, day boarder is a word with a broader meaning than dayboy:

dayboy: a day boarder who is a boy
day boarder: a schoolchild at a boarding school who has meals at school but sleeps at home

dayboy (noun)	day boarder (noun)
a day boarder who is a boy	a schoolchild at a boarding school who has meals at school but sleeps at home