1. [词根辨异]现在又遇到一对异源同形根：cern的异体cret1=to separate；cresc的异体cret2=to grow。请指出下列单词中词根cret的含义：
excretion discrete secretary concretion
accretion discretion concretive secretive
2. [由此及彼]比较下边两列的构词规律，填上相应的单词：
increase 增加 decrease 减少
① increment 增加量 ________________减少量
② increscent ________________渐盈的渐亏的
3. [词义判断]选择最恰当的词义。
① recreate A.改造 B.消遣 C.再生
② re-create A.改造 B.消遣 C.再生
③ procreate A.生殖 B.催生 C.代生
4. [寻根问底]指出下列单词的词根并领会其词义的由来。
① concrescence n.合生；增值
② decremeter n. [无]衰减计
③ decrescendo a. [音] 渐弱的
④ crescendo a. [音] 渐强的
⑤ accrete v.增大；合生
⑥ incrementalism n.渐进主义
20. cub, cumb [L]=to lie down躺
常用词incumbent，succumb，concubine和incubate是一组同根词。词根cub来自拉丁动词cubare，词根cumb来自拉丁动词cumbere；而cumbere和cubare实际上是同一个词的异体，意思都相当于英语的to lie down（躺，卧）。
incumbent [in-=upon在……之上；cumb=to lie down躺；-ent a.=-ing……的→“lying upon somebody躺在或赋予某人身上的”→] I a. lying or resting on（somebody）as an obligation作为责任的：It is incumbent on you to warn them.你有责任告诫他们。→Ⅱn. person on whom an obligation lies;one who holds public office负有责任者；任公职者：the struggle between the incumbents and the candidates现任者与候选人之间的斗争
▽incumbency [in-;cumb;-ency n.] n.责任；任职；职权
succumb [suc-（sub-）=under在……之下；cumb=to lie down躺倒→“to lie down under pressure, illness etc.在压力、疾病等之下躺倒”→] v.① give way;yield让步，屈服：We will not succumb to difficulties.我们决不向困难低头。② die死：He succumbed to cancer.他死于癌症。
concubine [con-=together共同；cub=to lie down卧；-ine n.=female女人→“woman who lies down together with a man与某男人同卧共宿的女人”→] n. woman who inhabits with a man without being married姘妇，情妇
▽concubinage [concubin(e);-age n.] n.情妇身份；非法同居
incubate [in-=on在……上；cub=to lie卧；-ate v.=to cause使……→“to cause (a hen, etc.) to lie on eggs 使（母鸡等）卧在卵上”→] v.①sit on eggs in order to hatch them孵卵，孵化：Even a good hen can't incubate a wooden egg.母鸡再好也孵不了木头蛋。② give form to;develop把……酝酿成熟；使发展：to incubate a plan 酝酿一个计划
▽incubation [incubat(e);-ion n.] n.孵化；酝酿
incubator [incubat(e);-or n.] n.孵化器
incubative [incubat(e);-ive a.] a.孵卵的；潜伏期的
incubus [in-=upon在……之上；cub=to lie down卧；-us n.=thing物→“thing inclined to lie down upon a person喜欢卧在人的身上的东西”→] n. evil spirit supposed to lie down upon sleeping persons;nightmare压在睡眠者身上的恶魔；梦魔：The debt is like an incubus on me.这笔债务使我梦寐不安。
cubicle [cub=to lie躺；-icle n.=small thing 小东西→“small room for lying down供躺下歇息的小房间”→] n.① small bedroom小卧室② any small room小室
▽cubicular [cub;-icular a.] a.寝室的
recumbent [re-=backward向后；cumb=to lie躺；-ent a.=-ing……的→] a. lying backward;reclining躺着的；斜卧的：recumbent statue雕塑的卧像
▽recumbency [recumben(t);-cy n.] n.斜卧；依靠
procumbent [pro-=forward向前；cumb=to lie躺；-ent a.=-ing……的→“lying forward向前卧着的”→] a. leaning forward;prostrate;prone前俯的；平卧的；爬在地下的：The man fell procumbent on the ground.那个人摔了个嘴啃泥。
