A clathrate or clathrate compound is a type of inclusion compound in which a guest atom, ion, or molecule is enclosed in a cage-like cavity formed by a host molecule or by an extended host lattice. The term is derived from the Latin clatratus, meaning 'with bars' or 'latticed'. According to the International Union of Pure and Applied Chemistry (IUPAC), clathrates are inclusion compounds "in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules".