Used as a generic term for the air surrounding the earth.
The air surrounding the earth as seen from the surface of the earth troposphere→the stratosphere→the mesosphere→the thermosphere→the exosphere
Moist air (Air containing water vapour). More than 99% of the air in the atmosphere is in the troposphere.
Main components of the air excluding the vapour are nitrogen, oxygen, argon and carbon dioxide.
Air that does not contain water vapour. Dry air is considered as the standard because the moisture present in the moist air changes with temperature.
Percentage composition of dry air is shown in the table below.