What is altitude and how does it relate to air pressure?

Altitude refers to the height of an object or point in relation to sea level or ground level. As altitude increases, air pressure decreases because the density of air molecules diminishes at higher elevations. This reduction in air pressure can affect breathing and the performance of engines and other equipment designed for lower altitudes. Consequently, at higher altitudes, the body may require time to acclimatize to the lower oxygen levels associated with decreased air pressure.