78 feet from baseline to baseline.
A tennis court from baseline to net is 39 feet, so 39+39 = 78 and 78/3 equals 26 yards.
From the baseline to the net, a tennis court is about 21 feet. This gives the person plenty of space to jump around in.
In tennis there is singles, and doubles. In both there is playing baseline/server, alley/net/volley.
Baseline magazine is a Tennis magazine published in South Carolina. The articles in the magazine feature pro tennis players like Chris Peek and Moutray McLaren.
It is the 12" mark at the 1/2-way point of the baseline used to distinguish 2 halves (and service boxes) of a tennis court; short mark that bisects baseline.
On the serve, it must be in the service box. Other shots will depend what type of tennis you are playing. In doubles the boundaries are the most outward side lines and the baseline. In singles it is the innermost sidelines and the baseline