The quality of being perpetual.

(law, singular only) The rule that prevents a testator or other transferor of property from controlling further transfer of his property more than twenty-one years after the death of anyone alive at the time of the original transfer who may have some interest in the transfer.

plural of rule against perpetuities

(physics) The motion of some hypothetical device that continues forever with no external input of energy, in violation of the laws of thermodynamics.

A license with no expiration date.

Causing itself to continue to exist.

(finance) A bond with no maturity date, paying coupons forever.

plural of perpetual bond

(marketing) A marketing strategy in which a maker of computer software or hardware repeatedly launches early versions of new products as a product development feedback method.

plural of perpetual check