The first three parts of the water cycle are evaporation, condensation and precipitation. The next three stages of the six-part cycle are surface runoff, infiltration and transpiration.
The process of evaporation changes water from a liquid to a gaseous state called water vapor. This is why any water left on a surface dries up by itself after a period of time. Some of the water in lakes, rivers and oceans also evaporates as the sun heats it. When water evaporates, it leaves the impurities behind.
Condensation is the opposite phenomenon, in which water vapor changes back into liquid water. This occurs when the temperature of the water vapor decreases. Small droplets of condensation remain airborne and form clouds or fog. Condensation changes to precipitation when the small droplets of condensation form larger drops and fall in the form of rain, snow, sleet or hail. When temperatures are so low that the precipitation freezes in midair, it forms snow, sleet or hail.
When rainwater collects on the ground, it seeks the lowest level. This is surface runoff; eventually, all of the water reaches the oceans and seas the process of evaporation begins again. Some of the water enters the soil through the process of infiltration. Transpiration, the final part of the cycle, takes place when plants absorb the infiltrated water; it moves through the stem into the leaves, and from there, it evaporates back into the air.