Ethers IUPAC system

Although epoxides are always considered to have their oxygen atom as part of a three-membered ring, the prefix epoxy in the IUPAC system of nomenclature can be used to denote a cyclic ether of various sizes. Thus... 

We have been using the common nomenclature of ethers, which is sometimes called the alkyl alkyl ether system. The IUPAC system, generally used with more complicated ethers, is sometimes called the alkoxy alkane system. Common names are almost always used for simple ethers. 

Simple (symmetrical) ethers have the general formula R—O—R or Ar—O—Ar mixed (unsymmetrical) ethers are R—O—R or Ar—O—Ar or Ar—O—R. The derived system names R and Ar as separate words and adds the word ether. In the IUPAC system, ethers (ROR) are named as alkoxy- (RO-) substituted alkanes. Cyclic ethers have at least one O in a ring. 

Two systems for naming ethers are allowed by IUPAC rules. Simple ethers with no other functional groups are named by identifying the two organic substituents and adding the word ether ... 

---