首先这几个词共同的root是tain=hold, keep, have以下几个prefix:re = back,againob,oc,of,op = toward,against,in the waysub, suc, suf, sup, sur, sus = under,below,from, secretly, instead ofco, cog, col, coll, con, com, cor = with,together那么现在来看retain的意思是保留，持有，继续拥有。强调的是这种拥有是持续性的，反复性的。to keep something; to continue to have something obtain的意思是获得，赢得。强调的是通过努力得来的。to get something, especially by making an effortsustain的意思是维持，支撑，承受。强调的是维系。一般承受这种压力的主体都是在下面默默的承受。to make something continue for some time without becoming less contain的意思是包含，容纳，含有的意思，就是把东西聚集到一起拥有。if something contains something else, it has that thing inside it or as part of it.这样我觉得是比较正确的理解方法。
清清河中
