volunteer n. someone who volunteers to do a job or to join the army 自愿者

That man is a volunteer fireman in this town. 那个人是这个镇里的志愿消防队员。

v. offer to do a job that is unpleasant, difficult, or dangerous 自愿从事

Two men volunteered to search for the missing climber.

两个人自告奋勇去寻找那位失踪的登山运动员。

radium n. a chemical element that gives off rays 镭

Radioactivity is a special quality of radium. 放射性是镭的一种特性。

sum n. an amount obtained as a result of adding numbers 总数;和

Eleven is the sum of six and five. 十一是六加五的和。

n. amount of money一笔(金额)

He paid a large sum for the house. 他出一笔巨款买了这所房子。

dam n.[c] a barrier constructed across a waterway to control the flow or raise the level of water 水坝;堤

There are several dams across the Huai River. 淮河上有几座水闸。

bring up look after and educate children, etc 教养;培养

I was brought up by my aunt. 我是我姑姑抚养成人的。

introduce to notice or consideration, mention 提出

Why don't you bring this up at the meeting? 你何不在会上提出这个问题?

horizon n. line where the earth or sea seems to meet the sky 地平线

The sun sank below the horizon. 太阳落到地平线以下了。

navigation n. the act of navigating; the passage of ships, etc. over the sea, etc. 航行;航海;航空

aerial navigation 空中航行;航空 ocean navigation 远洋航行

Korea n. peninsula in east Asia, extending south from northeast China 朝鲜;韩国

suggest vt. give someone an idea; say that something will be possible 建议;提议 I suggested that we (should) hold a meeting tonight. 我提议我们今晚开个会。

vt. bring to mind 使人想起;暗示

Smoke suggests fire. 有烟就有火。

accomplish vt. finish something; complete; carry out 完成;实现