* Formal: "Before the internet, people relied heavily on telephone directories to find phone numbers."
* Informal: "My grandma still uses a telephone directory to look up numbers, she says it's easier than searching online."
* Humorous: "My phone number is so easy to remember, it's like it was designed to be in the front of the telephone directory."
You can also use "telephone directories" in sentences about their past use or their current rarity:
* "Remember when telephone directories were so thick they doubled as doorstops?"
* "It's strange to think that telephone directories are practically extinct now."
Ultimately, the best way to use "telephone directories" in a sentence depends on the context and your intended meaning.