pairs 是一对，一双的意思，是量词，同类词就如下列词一样。a couple of（两个、一对）—a couple of days，a couple of players，a couple of times a cupful of（一满杯）—a cupful of jelly，a cupful of water a portion of（一份／客）a portion of duck，a portion of roast beef 具体的你可以参考如下问题的答案。http://zhidao.baidu.com/question/4181265.html?si=1
