-idium

A structure in a plant or animal.

Greek diminutive suffix ‑idion.

Examples are antheridium (Greek anthos, flower), the male sex organ of algae, mosses, ferns, fungi, and other non-flowering plants; basidium (Greek basis, stepping), a microscopic club-shaped spore-bearing structure produced by certain fungi; nephridium (Greek nephros, kidney), an excretory organ in many invertebrates; pyxidium (Greek puxis, box), a seed capsule that splits open so that the top comes off like the lid of a box. See also ‑ium.