The amount of matter contained in a body: A mass is measured in grams, kilograms (kg), or tons.

A body of air in the lower atmosphere, which is more or less at a constant temperature and moisture content, and is often bounded by cold and warm fronts.

Equal to the cosine of the zenith angle or that angle from directly overhead to a line intersecting the sun.

The air mass is an indication of the length of the path solar radiation travels through the atmosphere. An air mass of 1.0 means the sun is directly overhead and the radiation travels through one atmosphere (thickness).

The process of a gravitational collapse inside a gaseous mass or cloud: The Jean's mass is named after Sir James Jeans, a British physicist.

A regions on the Moon with a higher than normal gravitational field: Mascoms are probably a result of abnormally dense material just beneath the lunar surface.

The transfer of information among groups of individuals of a kind that cannot be transmitted from a single individual to another: Examples of mass communication include the spatial organization of army ant raids, the regulation of numbers of worker ants on odor trails, and certain aspects of the thermoregulation of nests.

An empirical relation between the mass and luminosity, both usually expressed in solar units, for main sequence stars: The mass-luminosity relation was predicted by Eddington in 1924.

For sunlike stars, the luminosity varies as the 3.5 power of the mass.

The power is smaller for lower mass stars.