Real Dictionary

Yellow Pages
Yellow Pages is a book that contains advertisements and phone numbers for businesses and organizations in a particular area, grouped according to the type of business they do. Compare White Pages.

Yellow Pages in American English
the section or volume of a telephone directory, usually printed on yellow paper, containing classified listings of subscribers according to business, profession, etc.
plural noun: a classified telephone directory or section of a directory, listing subscribers by the type of business or service they offer, traditionally printed on yellow paper

Yellow Pages in British English
plural noun: a classified telephone directory, often printed on yellow paper, that lists subscribers by the business or service provided