The density altitude is the altitude relative to standard atmospheric conditions at which the air density would be equal to the indicated air density at the place of observation. In other words, the density altitude is the air density given as a height above mean sea level.
Also asked, what factors affect the density of air?
Pressure, temperature and humidity all affect air density. And you can think of air density as the mass of air molecules in a given volume. Increasing air density increases your engine, propellor and wing's performance. Decreasing air density decreases performance.
What increases density?
Increasing the pressure on an object decreases the volume of the object and thus increases its density. Increasing the temperature of a substance (with a few exceptions) decreases its density by increasing its volume. This causes it to rise relative to more dense unheated material.
What are the factors that affect the density of water?
The two main factors that affect density of ocean water are the temperature of the water and the salinity of the water. The density of ocean water continuously increases with decreasing temperature until the water freezes. Ocean water, with an average salinity of 35 psu, freezes at 28.5oF (-1.94oC).