Samuel Groth has hit the fastest serve at 263 km/h.
120mph Roscoe Tanner
To serve in tennis, is to hit a tennis ball with your racquet, aiming to score against an opponent.
Venus Williams holds the record for fastest serve recorded by a female at 127 mph.
Roddick, Andy Roddick, Andy
no, a serve must be hit from out of the air
It depends on how hard you want to hit the ball
She would be Venus Williams at the 2007 US Open recorded at 129.0 mph (207.6 km/h)
On a personal level, it all depends on your skill. As a comparison, the fastest a professional has hit a forehand was 120 mph (by Gael Monfils), and 155 mph on a serve (by Andy Roddick).
Because you hit the ball with some kind of racket and that is why you call it a serve.
you throw the ball in the air and hit it