single entry vs bookkeeping

single entry and bookkeeping both are nouns.

Word	Noun	Adjective	Verb	Adverb
single entry	Yes	No	No	No
bookkeeping	Yes	No	No	No

As nouns, bookkeeping is a hypernym of single entry; that is, bookkeeping is a word with a broader meaning than single entry:

single entry: a simple bookkeeping system; transactions are entered in only one account
bookkeeping: the activity of recording business transactions

Other hypernyms of single entry include clerking.

single entry (noun)	bookkeeping (noun)
a simple bookkeeping system; transactions are entered in only one account	the activity of recording business transactions