Alveolus

[æl'viәlәs]

(noun.) a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways.

Editor: Priscilla--From WordNet

(n.) A cell in a honeycomb.

(n.) A small cavity in a coral, shell, or fossil

(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.

Checker: Roland

n. [L.] Alveole.

Typist: Margery