Courts described as fast or slow differ in measurable ways. Speed is a property of friction and rebound at the surface, and it can be adjusted deliberately during construction.
What speed actually means
When a ball lands, part of its forward momentum is lost to friction and part of its vertical energy is returned as bounce. Surfaces differ in both.
A low-friction surface preserves horizontal speed, so the ball skids through and the receiver has less time. A high-friction surface bites, slowing the ball and lifting it higher.
Bounce height matters as much as pace, because a ball rising into the strike zone is easier to attack than one staying low near the knees.
How hard courts are tuned
A hard court is a rigid base finished with acrylic layers containing sand or similar aggregate. The quantity and grade of that aggregate set the friction.
More aggregate produces a rougher, slower surface; less produces a smoother, faster one. The change is invisible to spectators and entirely within the tournament's control.
The underlying base also matters, since a stiffer construction returns more vertical energy and produces a higher bounce than a cushioned one.
Clay and grass behave differently
Clay is a loose top dressing over a compacted base. The ball slides into the surface, losing pace and rising steeply, and it leaves a mark that can be inspected.
Grass is the opposite. The ball skids off a firm, low-friction surface, and the bounce is lower and less consistent as the court wears through a fortnight.
Both surfaces change over the course of a tournament, which is why the same court plays differently in the second week from the first.
Why tournaments adjust speed
Speed influences which players succeed. Faster conditions reward serving and short points; slower conditions reward movement, defence and extended rallies.
Events also consider match length, since longer rallies make matches harder to schedule and can extend a session well beyond its broadcast window.
Adjustments are usually modest and rarely announced, but players notice immediately and comment on it during the opening days.
The ball is part of the system
Ball choice interacts with the surface. A larger or more heavily napped ball meets more air resistance and slows the game independently of the court.
Balls also change during play, fluffing up and losing pressure, which is why they are replaced at set intervals rather than when they look worn.
Court speed is therefore a combination of surface, ball and altitude, and comparing venues on the surface alone will mislead more often than it explains.
