1. lighten [ˈlaɪtn]
vt./vi.减轻，变轻；照亮，变亮
to become less dark
参考例句：
1. The sky began to lighten after the storm. 暴风雨后天空开始放晴。
2. They decided to lighten taxes. 他们决定减轻税收。
2. estimate [ˈestɪmət]
n.估计，估量；评价，看法；vt.估计，估量
to guess the cost , size , value , etc . of something
参考例句：
1. We estimate the cost to be five thousand dollars. 我们估计费用为5000美元。
2. The lowest estimate would put the worth of the jewel at $200. 按最低的评估这块宝石也值200美元。
3. gap [gæp]
n.缺口；间隔；差距；不足，缺陷
an empty space or opening in the middle of something or between two things
参考例句：
1. We must see that there is no gap in our defence. 我们必须确保我们的防御没有漏洞。
2. There is a gap of five miles between towns. 镇与镇之间相隔五英里。
4. exhibit [ɪgˈzɪbɪt]
vt.展览，展出，陈列；n.展览品；陈列品
to show something publicly
参考例句：
1. Next week those goods will exhibit in that shop. 下个星期，这些货物将在那家商店展出。
2. The economy continued to exhibit signs of decline in September. 9月份，经济继续呈现出衰退的迹象。
5. doubtful [ˈdaʊtfl]
adj.难以预测的，未定的；怀疑的，可疑的
If you are doubtful about something, you are uncertain about it
参考例句：
1. Let's try to clear up our difficult and doubtful points. 让我们设法把难处和疑点解决一下。
2. Everyone was doubtful at first,but his statement in detail held up. 起初大家都怀疑，但他的详细叙述证明情况属实。
6. reveal [rɪˈvi:l]
vt.揭露，泄露；展现，显示
to make known or show something that is surprising or that was previously secret
参考例句：
1. The journalist did not want to reveal the identity of his informant. 那个新闻工作者不想透露消息提供人的身份。
2. Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。
7. shift [ʃɪft]
n.交换，变化，移动，接班者；vt.更替，移转，变声；vi.改变，定责，更衣
to ( cause something or someone to) move or change from one position or direction to another, especially slightly
参考例句：
1. Lend me a hand to shift this box, will you? 来帮一下忙，把这箱子搬开，好吗？
2. A sudden shift in the wind warned of the coming storm. 风向的突然改变预示暴风雨来临。
8. reflection [rɪˈflekʃn]
n.映象，倒影；反射；反映；非议；深思
the image of something in a mirror or on any reflective surface
参考例句：
1. The reflection of the sun on the glass wall was blinding. 玻璃墙上反射的太阳光令人目眩。
2. One can see the reflection of the tower in the water. 塔的影子倒映在水中。
9. render [ˈrendə(r)]
vt.给予；提供(帮助等)；使得；使成为
to cause someone or something to be in a particular state
参考例句：
1. Any assistance you can render him will be appreciated. 无论给予他何种帮助，他都会非常感激。
2. We are going to render them economic assistance. 我们打算向他们提供经济援助。
10. continual [kənˈtɪnjuəl]
adj.不间断的，不停的；多次重复的，频频的
happening repeatedly , usually in an annoying or not convenient way
参考例句：
1. I am tired of this continual rain. 不停的下雨使我厌倦。
2. He has continual arguments with his father. 他屡次跟他父亲争论。
11. sufficient [səˈfɪʃnt]
adj.充足的，充分的
enough for a particular purpose
参考例句：
1. His income is sufficient for his needs. 他的收入能满足他的需要。
2. Have you had sufficient? 你吃饱了没有？
12. log [lɒg]
n.记录，圆木，日志；vt.伐木，切，航行；vi.伐木
a thick piece of tree trunk or branch , especially one cut for burning on a fire
参考例句：
1. They log for a living. 他们以伐木为生。
2. And then what do you do with that log? 然后你要拿那些记录做什么呢？
13. lens [lenz]
n.透镜，镜片；镜头
a curved piece of glass , plastic or other transparent material used in cameras , glasses and scientific equipment , which makes objects seem closer , larger , smaller ,
参考例句：
1. The lens of a camera forms images. 照相机的镜头使图像形成。
2. You should screen the lens of your camera from direct sunlight. 你应该保证相机的镜头不受到阳光的直接照射。
14. trace [treɪs]
n.痕迹，踪迹，微量；vt.追踪，找出根源，描绘；vi.追踪
to find someone or something that was lost
参考例句：
1. There isn't a trace of a smile on her face. 她脸上没有一丝笑容。
2. We have lost all trace of him. 我们找不到他的踪迹。
15. pinch [pɪntʃ]
n.捏，撮，困苦，偷窃；vt.掐，使...困苦，偷窃
to squeeze something, especially someone's skin , strongly between two hard things such as a finger and a thumb , usually causing pain
参考例句：
1. She would pinch on food in order to spend on clothing. 她过去常把伙食费省下来买衣服。
2. He put a pinch of salt on his food. 他在自己的食物上撒了一撮盐。
16. hay [heɪ]
n.(用作饲料或覆盖的)干草
grass which is cut , dried and used as animal food or as covering material
参考例句：
1. Cows feed on hay. 奶牛以干草为生。
2. They usually keep the hay in the barn. 他们通常将干草存放在谷仓中。
17. roughly [ˈrʌfli]
adv.概略地，粗糙地，粗鲁地
approximately
参考例句：
1. If you treat your coat so roughly, it will be worn out soon. 你如果这么糟蹋你的外套，它很快就不能穿了。
2. The island is roughly circular in shape. 这个岛屿大致是圆形的。
18. learned [ˈlɜ:nɪd]
adj.有学问的，博学的；learn的过去式和过去分词
describes someone who has studied for a long time and has a lot of knowledge
参考例句：
1. He went into a rage when he learned about it. 他听到这事后勃然大怒。
2. In this little village, he passed for a learned man. 在这个小村子里，他被视为有学问的人。
19. fraction [ˈfrækʃn]
n.小部分，碎片；一点，一些；分数
a number that results from dividing one whole number by another, or a small part of something
参考例句：
1. The car missed me by a fraction of an inch. 那车子差一点儿就要撞到我了。
2. The cost is only a fraction of his salary. 那项费用不过是他薪水的一小部分。
20. yield [ji:ld]
vt.生产，出产；让步，屈服；vi. 屈服，投降；n.产量，收获量
to supply or produce something positive such as a profit , an amount of food or information
参考例句：
1. A cow will yield several gallons of milk each day. 一头母牛每天产几加仑的牛奶。
2. We shall never yield to a conqueror. 我们永远不会向征服者低头。
