1.isotope n．同位素(两个或更多具有相同原子序数却具有不同的质量数的原子中的一个)(one of two or more atomic number but different mass numbers)

词根记忆：iso(等，同)+tope--同位素

例：heavy isotope重同位素

派生词：isotopic(a．同位素的)

2.jeopardize v.危及，危害(to expose to danger or risk)

词根记忆：jeopard (危险)+ize--使处于危险中--危及，危害

例：If too little attention is given to basic research today, future technological advancement will be jeopardized.

派生词：jeopardy(n.危险，危害)

3.judicial a．司法的(of, relating to, or proper to courts of law or to the administration of justice)；公正的(just)

词根记忆：judic（评判，法律）+ial--司法的；公正的

例：judicial rules司法规定

4.jumbo a．巨大的(unusually large)

联想记忆：本是一头大象的名字，代指“体大而笨拙的人”，作形容词用时意为“巨大的”

例：The development of a new jumbo rocket is expected to carry the U.S. into its next phase of space exploration.

5.jurisdiction n.管辖权(authority or control);管辖区域(the limits within which authority may be exercised)

词根记忆：juris(=jury法律）+dict(命令)+ion--按照法律享有命令权--管辖权

例：These islands are under U.S. jurisdiction. //One state adds a 7 percent sales tax to the price of most products purchased within its jurisdiction.

6.juror n.陪审团成员(a member of a jury)

词根记忆：jur(评判，法律)+or--按照法律评判的人--陪审团成员

例：Civil trials often involve great complexities that are beyond the capacities of jurors to understand.

7.justify v.证明…正当或有理(to prove or show to be just, right, or reasonable)

词根记忆：just(正义)+ify(使…)叶证明…正当（或有理）

例：Companies are never justified in employing young children, even if the child's family would benefit from the income.

派生词：justification(n．正当理由：辩护)：justifiably（ad.有理由地）：unjustified（a．未被证明正确的）

8.juvenile a．青少年的(youthful)

词根记忆：juven(年青)+ile --青少年的

例：Juvenile delinquency is a serious social problem.

同根词：rejuvenate(v.返老还童)

9.juxtapose v.并放，并列(to place side by side)

词根记忆：juxta(接近)+pose(放)--挨着放--并放，并列

例：The central idea is restated and juxtaposed with evidence that might appear to contradict it.

10.kernel n.果仁(the inner part of a nut or seed)；核心(most important part)

词根记忆：kern( =corn种子)+el--核心

例：Heating a wheat kernel destroys its gluten , a protein that must be present in order for yeast to leaven bread dough.

11.kidney n．肾脏

例：Desert rats' kidneys can excrete a urine having twice as high a salt content as sea water.

12.kin n.<集合词>家属，亲戚(relatives)

例：Self-help and the help of kin got most workers through jobless spells.

派生词：kinship(n.亲属关系)

13.kinetic a.运动的(of, relating to, or produced by motion)

词根记忆：kinet(动)+ic--运动的

例：kinetic energy动能

同根词：kinescope(n.显像管);kinematics(n．运动学)