Yarnstorming - Also called yarnbombing, an intriguingly specialised type of peaceful demonstration and activism in which objects such as works of art, sculpture, railings, phone boxes, considered unattractive by the activists, are covered by knitting or crochet, usually at night, and mainly by young women.

Yellow Pages  - A telephone directory, usually printed on yellow paper, which lists businesses, organisations, retailers, etc., in alphabetical order in categories according to the service they provide.

Yellow Sheets - Published every day in the US by the National Quotation Bureau, a list which shows information and prices of corporate bonds.

Yeoman - A servant or attendant in a royal or noble household.

Yield - The annual income earned from an investment, usually expressed as a percentage of the sum invested.

Youth Court - A court of law, which members of the public are not allowed to attend, that deals with juvenile (under 18 years of age) offenders.

Yuppie - Derives from Young Urban Professional. Term used since the 1980s to describe a young person who has a well-paid job and an affluent lifestyle.