单数表示谁的，形容词性或者名词性物主代词用's比如：Thedressismysister's.Mysister'sdressisverypretty.复数的形容词性或者名词性物主代词，表示谁的，用s'.比如Myclassmates'clothesaresoexpensive.或者Theexpensiveclothesbelongtomyclassmates'.
