How is density altitude defined?

Density altitude is defined as pressure altitude corrected for nonstandard temperature. This means that density altitude takes into account the actual temperature of the air compared to the standard temperature at a given pressure altitude.

In aviation, understanding density altitude is crucial because it directly affects aircraft performance, including lift and engine efficiency. As temperature increases or pressure decreases, air density decreases as well, leading to a higher density altitude, which can compromise an aircraft's performance in terms of climb rate, takeoff distance, and overall efficiency.

By using pressure altitude as a starting point and adjusting for temperature deviations from standard, you arrive at a more accurate representation of the "density" that the aircraft will experience, thus allowing pilots to make informed decisions regarding flight safety and aircraft performance.

The other choices don't accurately encapsulate the definition of density altitude as it pertains to both pressure and temperature adjustments.