A sealed, airtight chamber, such as in a manned spacecraft or submarine, used to provide access to and from the sealed area without allowing air out or water in.
A vestibule, foyer or entranceway with doors to the exterior on one end and doors to the interior on the other, functioning to keep indoor and outdoor air, humidity, and air temperatures separate.
Any enclosed body cavity or chamber.
An upper chamber of the heart that receives blood from the veins and forces it into a ventricle. In higher vertebrates, the right atrium receives blood from the superior vena cava and inferior vena cava, and the left atrium receives blood from the left and right pulmonary veins.
A cavity inside a porate aperture of a pollen grain formed by the separation of the sexine and nexine layers, widening toward the interior of the grain.
A cavity, entrance, or passage.
A microscopic air sac within a pulmonary alveolus.
A central room or space in ancient Roman homes, open to the sky in the middle; a similar space in other buildings.
A square hall lit by daylight from above, into which rooms open at one or more levels.