The atmosphere is the gaseous envelope of the Earth. It is made up of a mixture of gases which is called the air.
The characteristic vertical temperature profile of the atmosphere determines the most common way of dividing it. The lowest layer, the troposphere, plays a significant role.
This is where the majority of the mass of the atmosphere and the vast majority of atmospheric water are concentrated. Although the amount of atmospheric water is negligible compared to the other components of the atmosphere, it is extremely important in the hydrological cycle and energy transfers.