Atmospheric pressure is the force per unit area exerted on the Earth's surface by the weight of the atmosphere. There are many synonyms for atmospheric pressure that can be used depending on the context. Some of the synonyms for atmospheric pressure are barometric pressure, air pressure, environmental pressure, and atmospheric weight. Barometric pressure is often used to describe the pressure measured by a barometer, while air pressure is a more general term referring to the pressure exerted by air molecules. Environmental pressure may be used in discussions about the effects of atmospheric pressure on the environment, and atmospheric weight refers to the weight of the atmosphere itself.