What is the definition of air pressure?

Air pressure is defined as the force exerted by the weight of air molecules per unit area. This means that air pressure is not simply about the weight of the atmosphere above a particular point on the Earth's surface, but specifically the force that these air molecules apply to a given area.

The concept encompasses how atmospheric gases interact with surfaces, which is influenced by various factors such as temperature, volume, and the number of air molecules present. Thus, describing air pressure in terms of force per unit area accurately captures the dynamic nature of how atmospheric gas particles exert pressure in all directions.

In contrast, while the weight of the atmosphere on the Earth's surface is related, it is a broader concept that doesn't specifically frame the interaction in terms of force per area. The density of air molecules pertains to how closely packed the molecules are, which relates to pressure but does not define it outright. Additionally, temperature at sea level does not provide information relevant to air pressure specifically, as pressure can vary independently of temperature across different altitudes and conditions.