Air, like any other fluid, obeys certain laws. For example, if you blow smoke around the outside of a glass tube, the smoke (also a kind of fluid) will follow the contours of the tube. That is, the smoke will wrap around the two sides of the tube and meet at the other side. Let's call this "flow," since it has to do with the way fluids flow around solid objects.
Fluids also like to spread out as far as possible. That is, fluids under higher pressure (where the molecules are closer together) tend to push out with greater force than fluids under lower pressure (where the molecules are spread out). Let's call this "spread."
Wind is an example of spread. You've probably seen a weather map with high- and low-pressure systems: When they meet, the air under high pressure pushes out into the area of low pressure. We call that movement wind.
2torials:
Learnlets: