The bony socket in which the root of a tooth resides.
The socket of a macrotrichium (seta).
An acinus (saclike cavity) in a gland.
Any of the many tiny air sacs in the lungs in which the bronchioles terminate and where oxygen and carbon dioxide are rapidly exchanged with the pulmonary capillaries.
A nodule of stone having a cavity lined with mineral or crystal matter on the inside wall.