codex vs leaf-book

codex and leaf-book both are nouns.

Word	Noun	Adjective	Verb	Adverb
codex	Yes	No	No	No
leaf-book	Yes	No	No	No

As nouns, codex and leaf-book are synonyms defined as:

codex and leaf-book: an unbound manuscript of some ancient classic (as distinguished from a scroll)

codex (noun)	leaf-book (noun)
an unbound manuscript of some ancient classic (as distinguished from a scroll)	an unbound manuscript of some ancient classic (as distinguished from a scroll)
an official list of chemicals or medicines etc.