1. 地球（指宇宙组成部分时用Earth，指人类居住的星球时用the Earth）
    Earth or the Earth is the planet on which we live. People usually say Earth when they are referring to the planet as part of the universe, and the Earth when they are talking about the planet as the place where we live.

    e.g. The space shuttle Atlantis returned safely to earth today. “
           亚特兰蒂斯”号航天飞机今天安全返回地球。
    e.g. ...a fault in the Earth's crust.
           地壳断层

2. 陆地;地面
    The earth is the land surface on which we live and move about.

    e.g. The earth shook and the walls of neighbouring houses fell around them.
           地面摇晃，周围房屋的墙体在他们身边倒塌。

3. 泥土;土壤;土地
    Earth is the substance on the land surface of the earth, for example clay or sand, in which plants grow.

    e.g. The road winds for miles through parched earth, scrub and cactus...
           公路蜿蜒数英里，穿过炙烤的大地、灌木丛和仙人掌。
    e.g. They will revert to tilling the earth in an old-fashioned way.
           他们将回归到用老方法耕地。

4. （狐等的）洞穴
    An earth is a hole in the ground in which an animal such as a fox lives.

5. （接）地线
    The earth in an electric plug or piece of electrical equipment is the wire through which electricity can pass into the ground, which makes the equipment safe if something goes wrong with it.

earth

    e.g. The earth wire was not connected.
           地线没有接上。

6. see also: down-to-earth

7. （用于以how, why, what 或 where 开始的问句，表示强调，通常表示问题没有答案或很难回答）究竟，到底
    On earth is used for emphasis in questions that begin with words such as 'how', 'why', 'what', or 'where'. It is often used to suggest that there is no obvious or easy answer to the question being asked.

    e.g. How on earth did that happen?...
           那件事到底怎么发生的？
    e.g. What on earth had Luke done?...
           卢克究竟做了什么？

8. （用于否定名词短语后表强调）根本，完全
    On earth is used for emphasis after some negative noun groups, for example 'no reason'.

earth的反义词

    e.g. There was no reason on earth why she couldn't have moved in with us...
           她没能搬过来和我们同住，这根本就说不通。
    e.g. There is no feeling on earth like winning for the first time.
           初尝胜利滋味的感觉真是无可比拟。

9. (用于包含形容词最高级的名词短语后表示强调)世界上，人世间
      On earth is used for emphasis after a noun group that contains a superlative adjective.

      e.g. He wanted to be the fastest man on earth.
             他想成为世界上跑得最快的人。
      e.g. ...the site of the worst ecological disaster on earth.
             世界上最严重的生态灾难发生地

10. （激动之后）恢复正常生活，回到现实
      If you come down to earth or back to earth, you have to face the reality of everyday life after a period of great excitement.

      e.g. When he came down to earth after his win he admitted: 'It was an amazing feeling'...
             从胜利的喜悦中平复后，他承认：“当时感觉棒极了。”
      e.g. I was shocked, brought down to earth by this revelation.
             真相的披露让我深感震惊，我被带回了现实。

11. （经过长时间的寻找后）终于找到
      If you run someone or something to earth, you find them after searching for them for a long time.

      e.g. She ran him to earth in the pub at five to one.
             1点差5分的时候，她终于在酒馆里找到了他。

12. 价格不菲/斥巨资
      If you say that something cost the earth or that you paid the earth for it, you are emphasizing that it cost a very large amount of money.

      e.g. It must have cost the earth.
             这肯定花了很多钱。

13. hell on earth -> see hell
      to move heaven and earth -> see heaven
      salt of the earth -> see salt