Which number is traditionally worn by a rugby union scrum-half?

The scrum-half traditionally wears number 9 in rugby union.

The scrum-half links the forwards and backs, usually passing the ball from rucks, mauls, scrums and lineouts to the fly-half or another back. The position demands quick decisions, accurate passing and strong communication because the scrum-half often controls the speed of attacking play.

Numbering conventions developed from positional formations rather than from fixed squad rankings. Number 9 became associated with the scrum-half, while number 10 traditionally identifies the fly-half, the player who often directs the backline and makes tactical kicking decisions.

Modern rugby allows greater flexibility, and squad numbers may differ in some competitions or specialist formats. Nevertheless, in the standard 15-player shirt-number system, the scrum-half remains number 9. The position is sometimes called half-back, especially in descriptions of older rugby traditions.