telephone book vs telephone directory

telephone book and telephone directory both are nouns.

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

As nouns, telephone book and telephone directory are synonyms defined as:

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

Other synonyms of telephone book include phone book, phonebook.

telephone book (noun)	telephone directory (noun)
a directory containing an alphabetical list of telephone subscribers and their telephone numbers	a directory containing an alphabetical list of telephone subscribers and their telephone numbers