Air density refers to the mass of air per unit volume, typically expressed in kilograms per cubic meter (kg/m³). It is influenced by factors such as temperature, pressure, and humidity. As temperature increases, air density decreases because warmer air expands and occupies more space. Conversely, higher pressure compresses air, increasing its density. Air density plays a crucial role in various fields, including meteorology, aviation, and environmental science. For example, in aviation, lower air density at high altitudes affects aircraft performance, requiring adjustments in lift and engine power. Understanding air density helps scientists and engineers make informed decisions in their respective areas.