(physics, chemistry) The total number of protons and neutrons in an atomic nucleus. Symbol: A

The starvation of a large proportion of a region's population due to drought, warfare, famine or similar events.

(aerospace) The total mass of the burnt fuel etc. ejected from a rocket to provide thrust.

(physics) The increased mass of an object moving at relativistic speed relative to an observer.

(physics) The mass of a body when it is not moving relative to an observer.

(chemistry) The mass of an individual molecule of an element or compound.

(physics) The amount of fissile material needed to support a self-sustaining nuclear chain reaction. / (figuratively) The tipping point.

(physics, analytical chemistry) An analytical technique that measures the mass / charge ratio of the ions formed when a molecule or atom is ionized, vaporized and introduced into a vacuum. Mass spectrometry may also involve breaking molecules into fragments - thus enabling its structure to be determined.

Collectively, the communications media, especially television, radio, and newspapers, that reach the mass of the people.

(military) A body of troops held in military reserve by a general for striking a blow on an exposed flank or wherever the enemy reveals a weak spot.