encyclopaedia vs reference work

encyclopaedia and reference work both are nouns.

Word	Noun	Adjective	Verb	Adverb
encyclopaedia	Yes	No	No	No
reference work	Yes	No	No	No

As nouns, reference work is a hypernym of encyclopaedia; that is, reference work is a word with a broader meaning than encyclopaedia:

encyclopaedia: a reference work (often in several volumes) containing articles on various topics (often arranged in alphabetical order) dealing with the entire range of human knowledge or with some particular specialty
reference work: a book to which you can refer for authoritative facts

Other hypernyms of encyclopaedia include book of facts, reference, reference book.

encyclopaedia (noun)	reference work (noun)
a reference work (often in several volumes) containing articles on various topics (often arranged in alphabetical order) dealing with the entire range of human knowledge or with some particular specialty	a book to which you can refer for authoritative facts