estates. In Pennsylvania, this term is used to signify a perpetual rent issuing out of some real estate. This rent is redeemable where there is a covenant in the deed that, before the expiration of a period therein named, it may be redeemed by the payment of a certain sum of money; or it is irredeemable, when there is no such agreement; and, in the latter case, it cannot be redeemed without the consent of both parties.