An epoxide is an ether in which the oxygenatom is part of a ring of three atoms. This ring is approximately an equilateral triangle, i.e. its bond angles are about 60°, which puts it under strain. The strained ring makes epoxides more reactive than other ethers.
A polymer made of epoxide units is called a polyepoxide or an epoxy. Epoxy resins are used as adhesives and structural materials.
