两个术语之间的差别在于estate on conditional limitation (也称为contingent estate)是指当某种紧急事件发生时才允许对财 产权益转让予以限制，即财产权益将从原受让人手中转为授予其他人，但如紧急情况不发生，则不会出现对财产权益的转让进行限制的情况，故为“受意外条件限制的权益”[1]。相比之下，estate subject to a conditional limitation 则主要指一种时间上的限制，即即使不发生紧急情况，到时也会对财产权益转让予以限制，故为“受时间限制的权益”[2]。
    
[1]“An estate conveyed to one person so that，upon occurrence or failure of occurrence of some contingent event, whether conditional or limitative，the estate shall depart from original grantee and pass to another. ”Cf. The Publisher's Editorial Staff, Black's Law Dictionary, abridged 6th edition, at pp. 381 -382, West Publishing Co. (1991 )
[2]“The distinction between an estate upon condition subsequent and an estate subject to a conditional limitation is that in former words creating condition do not originally limit term，but merely permit its termination upon happening of contingency，while in latter words creating it limit continuation of estate to time preceding happening of contingency. ”Id. at p. 382.