(physics, chemistry) A conservation law of classical physics that states that the total mass of a closed system remains constant regardless of the chemical or physical changes that take place within it.

Method of transport, usually public, that carries people in greater quantities than a typical private method such as car.

Of a product: produced in large numbers, and designed to appeal to many different people.

The killing of a large number of people over a short period of time.

plural of mass noun

Burial of multiple bodies in a mass grave

A device used in mass spectrometry to discover the mass spectrum of a given substance.

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

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

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