The words tall and short refer to the vertical extent of something. So we call a person with a greater vertical extent tall and lesser short. But this can be misleading, as there are much greater differences than merely vertical extent between short and tall people. In fact, the fundamental properties of the body vary with height.
For example, the taller body is absolutely stronger but relatively weaker as per the square-cube law. Similarly, the taller body uses more energy in the absolute sense, but less in the relative sense.
Many other aspects of the body change. For example, longer nerves makes for slower reflexes.
How the body scales is an often debated matter. Sometimes it is thought to scale not proportionally but with the square of height (Body Mass Index). But this is incorrect and leads to the labeling of healthy tall people as overweight. The solution is the Better Body Mass Index.