The word oyster is used as a common name for a number of different families of Terran saltwater clams, bivalve molluscs that live in marine or brackish habitats. In some species the valves are highly calcified, and many are somewhat irregular in shape. Many, but not all, oysters are in the superfamily Ostreoidea.
Some kinds of oysters are commonly consumed, cooked or raw, by people as a delicacy. Some kinds of pearl oysters are harvested for the pearl produced within the mantle. Windowpane oysters are harvested for their translucent shells, which are used to make various kinds of decorative objects.
In the Union, 99% of all oysters are cultivated and destined to be consumed. Terra is still the largest producer of oysters.