Someone who is not a legal adult, and thus should be treated as a minor. 

Different organisations should set their own definitions of the age at which someone stops being a young person. But an acceptable and pragmatic default would seem to be at the age that both marks the start of practical majority and the Arts Council England ‘Family Friendly’ initiative’s definition of a child. This is 16 years of age or less. (See the related protocol for below.)

This protocol should be used whenever an arts organisation wishes to segment, research and report on discrete groups within its audiences, attenders and visitors.

Richard Ing [2001] Funky on Your Flier: A Report on the ‘Crossing the Line’ Seminars, London: Arts Council England, p. 5. Downloadable from the Arts Council of England.

The Electoral Commission [2004] Age of Electoral Majority: Report and Recommendations, London: The Electoral Commission. Downloadable from here.