telephone book vs directory

telephone book and directory both are nouns.

Word	Noun	Adjective	Verb	Adverb
telephone book	Yes	No	No	No
directory	Yes	No	No	No

As nouns, directory is a hypernym of telephone book; that is, directory is a word with a broader meaning than telephone book:

telephone book: a directory containing an alphabetical list of telephone subscribers and their telephone numbers
directory: an alphabetical list of names and addresses

telephone book (noun)	directory (noun)
a directory containing an alphabetical list of telephone subscribers and their telephone numbers	an alphabetical list of names and addresses
	(computer science) a listing of the files stored in memory (usually on a hard disk)