1. That is actually a cavity in the earth.
    那其实是一个地下洞穴。

2. cavity的解释

2. Cavities in teeth are caused by decay.
    牙齿的蛀洞是由蛀蚀造成的。

1. 空洞：6.空洞与空腔 空洞(cavity)为肺内病变组织发生坏死,坏死组织经引流支气管排出而形成. X线表现为大小与形状不同的透明区(图3-1-13). 见于肺结核的干酪样坏死病变、肺脓肿、肺癌及某些真菌病. 空洞壁可由坏死组织、肺脓肿、肺癌及某些真菌病.

1. 洞;孔;腔
    A cavity is a space or hole in something such as a solid object or a person''s body.

2. (牙科)龋洞，蛀牙洞
    In dentistry, a cavity is a hole in a tooth, caused by decay.

1. (anatomy) a natural hollow or sinus within the body

    Synonym: bodily cavitycavum

2. a sizeable hole (usually in the ground)

    e.g. they dug a pit to bury the body

    Synonym: pit

3. soft decayed area in a tooth
    progressive decay can lead to the death of a tooth

    Synonym: cariesdental cariestooth decay

4. space that is surrounded by something

    Synonym: enclosed space