account book vs daybook

account book and daybook both are nouns.

Word	Noun	Adjective	Verb	Adverb
account book	Yes	No	No	No
daybook	Yes	No	No	No

As nouns, daybook is a hyponym of account book; that is, daybook is a word with a more specific, narrower meaning than account book:

Other hyponyms of account book include cost ledger, general ledger, subsidiary ledger, journal.

account book (noun)	daybook (noun)
a record in which commercial accounts are recorded	an accounting journal as a physical object
	a ledger in which transactions have been recorded as they occurred