Eng: Hollow...

凹

Concave, Dented, Depression, Hollow, Indentation

膕

Hollow, Popliteus

窩

Apartment, Bend, Block, Brood, Cave, Check, Crease, Den, Hold in, Hollow, Litter, Living, Nest, Pit, Restrain

空

Air, Bare, Deserted, Empty, Have free time, Hollow, In vain, Sky, Space

虛

Empty, False, Hollow, Pretend, Unreal, Virtual, Void

坳

Cavity, Depression, Hollow

鏤空

Hollow

中空

Hollow