perpetuity

noun4

1. •
   The quality or state of being perpetual; endless duration; uninterrupted existence.
2. •
   Something that is perpetual.
3. •
   An annuity in which the periodic payments begin on a fixed date and continue indefinitely.
4. •
   A limitation intended to be unalterable and of indefinite duration; a disposition of property which attempts to make it inalienable beyond certain limits fixed or conceived as being fixed by the general law.