Vocal range
A boy soprano is a young male singer with an unchanged voice in the soprano range. Although a treble, or choirboy, may also be considered to be a boy soprano, the more colloquial term boy soprano is generally only used for boys who sing, perform, or record as soloists, and who may not necessarily be choristers who sing in a boys' choir.

Origins

In the liturgical Anglican and English Catholic traditions, young choristers are normally referred to as trebles, rather than boy sopranos. The term "treble" derives from the Latin triplum, used in 13th century motets to indicate the third and highest range. Trebles have an average range of C4-A5.