leaf vs flyleaf

leaf and flyleaf both are nouns.

Word	Noun	Adjective	Verb	Adverb
leaf	Yes	No	Yes	No
flyleaf	Yes	No	No	No

As nouns, flyleaf is a hyponym of leaf; that is, flyleaf is a word with a more specific, narrower meaning than leaf:

leaf: a sheet of any written or printed material (especially in a manuscript or book)
flyleaf: a blank leaf in the front or back of a book

Other hyponyms of leaf include interleaf, page.

leaf (noun)	flyleaf (noun)
hinged or detachable flat section (as of a table or door)	a blank leaf in the front or back of a book
a sheet of any written or printed material (especially in a manuscript or book)
the main organ of photosynthesis and transpiration in higher plants

leaf (verb)	flyleaf (verb)
produce leaves, of plants
turn over pages
look through a book or other written material