Alveolus :: Alveolus (n.) A small cavity in a coral, shell, or fossil.
Alveolus :: Alveolus (n.) A small depression, sac, or vesicle, as the socket of a tooth, the air cells of the lungs, the ultimate saccules of glands, etc..
Interalveolar :: Interalveolar (a.) Between alveoli; as, the interalveolar septa between adjacent air cells in the lungs..