C 洞穴 hollow place in the side of a cliff or hill, or underground

　cave　可指天然的山洞、崖洞或动物的地下洞穴，也指人工开凿的窑洞或地窖。

　explore a ～　勘探山洞
　deep ～　深深的洞穴
　～ man　石器时代的穴居人
　～ period　穴居时代

　The pupal cave was very big.　那蛹洞很大。
　The children found a cave in the side of the mountain.　孩子们在山坡上发现了一个岩洞。
　They picked a cave for their night camp.　他们选了一个山洞作为过夜的营地。
　She evaded her pursuers by hiding in a cave.　她藏到洞里避开了追赶她的人。
　They buried the treasure in the cave.　他们把宝物埋在山洞里。
　He asked me to hide it at the bottom of the cave.　他要我把它藏在洞穴底部。
　The force of the blast dashed him against the wall of the cave.　气浪的力量使他撞到窑洞的墙上。
　A winding path leads to the cave.　一条曲折小道通向山洞。
　They blocked up the entrance to the cave with big rocks.　他们用大石头堵住了洞口。
　He said it was called pupal caves.　他说这称为蛹洞。
　Many, many years ago man lives in caves.　很久很久以前，人类住在山洞里。
　Bears hibernate in caves during the winter.　冬季熊在洞穴中冬眠。
　The cave men lived in a period of history antecedent to written records.　穴居人生活在有文字记载之前的一个历史时期。

 ♣ cave, cavity, hole
　这组词都有“洞”“孔”“穴”的意思。其区别在于：hole指任何物体中的开口、穿孔或洞穴；cave指山洞、洞穴或地窖；cavity是科技术语或专门用语，只指坚硬物体上的洞穴，通常表面有开口可见。例如：
　The men have dug a hole in the road.　那些人在路上挖了一个洞。
　The cliff dwellers found that natural caves gave them warmth and protection during the Ice Age.　悬岩洞人发现在冰河时代天然的洞穴不仅温暖，还能借以自卫。
　The pleural cavity is a body where the lungs are situated.　胸膜腔是人体内肺脏所在的地方。
 ♣ cave, cavern
　这两个词都可作“洞穴”解。其区别在于：cave表示天然的或人为的“洞穴，山洞，窑洞”; cavern则指地下的巨穴或大的钟乳石岩洞，尤指巨大而昏暗的深穴。

1. vt. & vi.（使）塌陷；倒塌　 (cause to) fall in; give way to pressure
2. vi.屈服　 give in

　～ in　坍塌，倒闭，屈服
　～ in the bank　决堤
　～ in the hat　使帽子塌陷
　～ in the roof　使屋顶塌陷

　His cellar caved.　他的地窖塌陷了。
　Cave the dog!　当心狗！

 ♣ cave in　(v.+adv.)
　〔说明〕 cave in通常不用于被动结构。
1. 坍陷；塌方 fall inwards
　The roof of the tunnel caved in.　隧道的顶部塌陷了。
　The roof is dangerous and could cave in at any time.　屋顶很危险，任何时候都可能坍塌。
　The mine which caved in during the earthquake was soon repaired and resumed production.　在地震中坍陷的矿井很快修复了，并恢复了生产。
　Who has caved my hat in?　谁把我的帽子弄塌下去了?
　They caved in the roof of the underground passage with powerful explosives.　他们用强大的炸药把地下通道的顶部炸塌陷了。
2. （指商店等）倒闭 (of a business, etc.) fail
　Why do you want to appoint this man as manager?The last firm he worked for caved in.　你为什么要任命此人为经理?他所服务的前一个商行倒闭了。
3. 投降；屈服 fail; yield
　The children begged their father to take them to the circus until he caved in.　孩子们请求父亲带他们去看马戏，直到他让步为止。
　As we set forth facts and reasoned things out the criminal could not but cave in and admit his crime.　由于我们摆事实、讲道理，那个犯罪分子不得不低头认罪。
　They refused to cave in to the terrorists' demands.　他们拒绝向恐怖分子的要求屈服。
　The opposition caved in before our superior argument.　反对者在我们强有力的辩论之下屈服了。
　The challenger caved in during the seventh round.　竞争进入第七轮那位挑战者就一蹶不振了。

 ♣ cave, cavern
　这两个词并非同义词。cave的意思是“挖洞，塌陷”，常用作不及物动词；而cavern作“将…置入洞中，将…挖掘出来”解，用作及物动词。

　［同义词］ n. cavern, grotto, hole, speleology, spelunker v. collapse, fall in, give in
　［词源］　古法语和拉丁语cava（洞穴）