(evolutionary theory, geology) A sharp decrease in the total number of species in a relatively short period of time; specifically, a loss of ∼75% of all species on the planet over a geologically interval of less than 3 million years, as a result of a mass extinction event.

Any means of public communication that reaches a large audience.

Alternative form of en masse

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

(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.

plural of mass noun

plural of mass murder

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

Someone who commits a mass murder.