n.[C]

1. 洞，穴，凹處
   That is actually a cavity in the earth.

   那其實是一個地下洞穴。

2. （身體的）腔
3. （病變形成的）空洞；（牙的）蛀洞
   Cavities in teeth are caused by decay.

   牙齒的蛀洞是由蛀蝕造成的。

n.