Perpetuity

The quality of indefinite duration without change; the quality by which an estate becomes inalienable either perpetually, or for a very long period; a modification of an estate by which it ie made inalienable perpetually or indefinitely; a modification of an estate by which it is made inalienable beyond the period allowed by law, — the period of a life or lives in being and twenty-one years with the term of gestation added in case of a posthumous child; tht estate so modified or perpetuated.