the quality of lasting for a very long time, such as forever;
e.g. This torch will be kept burning in perpetuity, as it has been for hundreds of years.
(noun)
an agreement such as a bond or another security that does not have a fixed maturity date, essentially resulting in a stream of cash payments with no end;
e.g. Perpetuities have no fixed date of maturation and therefore serve as an endless cash stream.