directory vs phonebook

directory and phonebook both are nouns.

Word	Noun	Adjective	Verb	Adverb
directory	Yes	No	No	No
phonebook	Yes	No	No	No

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

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

Other hyponyms of directory include phone book, telephone book, telephone directory, blue book.

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