Dust is a general name for minute solid particles of diameters less than 500 micrometers (otherwise see sand or granulates) and, more generally, for finely divided matter. On Earth, dust occurs in the atmosphere from various sources: soil dust lifted up by wind, volcanic eruptions, and pollution are some examples. Dust is also widely present in outer space (see interstellar dust and Zodiacal light), where gas and dust clouds are primary precursors for planetary systems.

The dust which collects in homes is composed of the atmospheric dust combined with the dust generated by the inhabitants, mostly from sloughed skin cells and fibers from clothing and coverings. It is removed with a broom, dusting cloth, or vacuum cleaner.

Dust physical behaviour follows laws that are not always comparable with that of solid or fluid matter. For example the pressure on a box full of dust need not be uniform (See physics of granulate matter for explanation).

See also: dust storm.