In cricket, scoring six runs with one legal hit is called a six.
A six is awarded when a batter strikes the ball and it crosses the boundary without first bouncing inside the field. The ball may touch the boundary rope or the ground beyond it, but it must remain airborne until it has passed over the boundary. The six runs are credited to the batter and the team.
This differs from a four, which generally occurs when the ball reaches or crosses the boundary after bouncing or rolling on the ground. “Boundary” is the broader category covering both fours and sixes, so calling every boundary a four is technically incorrect. A six can also be scored when the batter clears the boundary directly, without running between the wickets.
The word “legal” matters: a no-ball is an illegal delivery and can produce a different score, such as a no-ball extra plus batting runs. Six runs cannot normally be recorded as extras from a ball that the batter never hit. Historically, sixes were once associated specifically with hits out of the ground; the modern boundary rule is broader.