1.rigorous a．严格的(manifesting, exercising, or favoring rigor)
词根记忆：来自rigor(n．严酷，严格)
例：Historians began to apply less rigorous scientific research criteria to the study of women's history.

派生词：rigorously( ad.严厉地)

2.rim n．边(brink);轮辋(the outer part of a wheel joined to the hub usually by spokes)

例：circular rim轮辋

3.rinse v.冲洗（to clean by flushing with liquid）
联想记忆：rin(=rain下雨)+se--雨水冲刷着地面冲洗

例:Tom rinsed his toothbrushes in the cold water.

4.ripple v.（使）起波纹（to become lightly ruffled or covered with small waves）；传开(spread)；n．波纹(dimple)
联想记忆：谜语( riddle)变dd为pp--波纹(ripple)

例：：The rain rippled the surface of the lake.//The lake was covered with small ripples.

5.ritual n．（宗教等的）仪式(ceremony)；a．仪式的(ceremonial)

例：Many rituals rise from mythical beliefs.//In the Western Zhou Dynasty only emperors were allowed to perform the ritual worship of heaven.

6.rival n．竞争者(competor)；可与匹敌的人（物）(peer);a．竞争的(competing)；v.比得上(match)
联想记忆：对手( rival)隔河(river)相望，分外眼红
例：The boxer vowed to beat any rival who challenged him.//It promotes healthy competition between rival industries.//Anne's paintings rival the ones I see in art galleries.

派生词：rivalry(n．竞争；敌对)

7.rivalry n.竞争，对抗(the state of being a rival)
词根记忆：来自rival(n．对手；竞争)
例：Within the boundaries of artistic rivalry lies a sense of family: the shared genetic inheritance, or accident, that enables musicians to make music.

派生词：rivalrous(a．敌对性的；有竞争性的)

8.robust a．健壮的(having or exhibiting strength)
联想记忆：中国的“乐百氏”(Robust)矿泉水就是这个单词

例：A large rise in the number of houses starting in the coming year should boost new construction dollars by several billion dollars, making the construction industry's economic health much more robust than it was five years ago.

9.rodent n.啮齿类动物(any of an order of relatively small gnawing mammals that have in both jaws a single pair of incisors with a chisel-shaped edge)
词根记忆：rod(咬)+ent--喜欢咬的动物--啮齿类动物
例:In some cities, recyclable trash is allowed to accumulate to attract rodents.
同根词：erode(v.侵蚀)；corrode(v.腐蚀)