A mule is a cross between a donkey and a horse. Therefore, a mule will have some donkey characteristics such as large ears, a head just a bit too large for its body, a skimpie â¦ r tail, some still have the cross on their backs from the donkey, and they often have small looking feet.
Density of air. The density of air, Ï (Greek: rho) (air density), is the mass per unit volume of Earth's atmosphere, and is a useful value in aeronautics and other sciences. Air density decreases with increasing altitude, as does air pressure. It also changes with variances in temperature or humidity.
Definition of DENSITY. 1. : the quality or state of being dense. 2. : the quantity per unit volume, unit area, or unit length: as a: the mass of a substance per unit volume b: the distribution of a quantity (as mass, electricity, or energy) per unit usually of space (as length, area, or volume).