(retronym, linguistics) Any human language that has evolved naturally in a community, usually in contrast to computer programming languages, to controlled natural languages, and to constructed languages such as Esperanto (although constructed languages are subject to change by natural forces among fluent speakers).

Turning away from urban environs and attitudes, towards an organic, agrarian lifestyle.

(mathematics) The logarithm in base e: either the function that given x returns y such that eʸ = x, or the value of y given by the function.

(biochemistry) Any compound produced naturally by a living organism; especially those compounds that are useful commercially

(immunology) A natural killer cell

Any source of wealth that occurs naturally, especially minerals, fossil fuels, timber, etc.

The fundamental set of qualities, and the range of behaviour, shared by all humans.

Any science involved in studying phenomena or laws of the physical world: physics, chemistry, biology, astronomy, and so on.

An image depicting inanimate objects; a still life.

Any natural phenomenon that causes great damage and loss of life. / The emergency situation that is the consequence of such an event.