Rain

Rain is a form of precipitation, as are snow, sleet, hail, dew and fog. Rain
forms when separate drops of water fall to the Earth's surface from clouds.
Not all rain reaches the surface, however; some evaporates while falling
through dry air, a type of precipitation called virga.

Rain plays a major role in the hydrologic cycle in which moisture from the
oceans evaporates, condenses into clouds, precipitates back to earth, and
eventually returns to the ocean via streams and rivers to repeat the cycle again.

The amount of rainfall is measured using a rain gauge. It is expressed as
the depth of water that collects on a flat surface, and is measured to the
nearest 0.25mm.

Falling raindrops are often described as "tear-shaped", round at the bottom
and narrowing towards the top, but this is incorrect. Small raindrops are
nearly spherical. Larger ones become increasingly flattened, like hamburger
buns; very large ones are shaped like parachutes. Large raindrops fall
faster than small ones.

Several cultures have developed a great aversion to rain and have developed
numerous protection devices such as umbrellas and rain coats. Many people
also prefer to stay inside on rainy days.