Rule 1. Ethers can be named as alkoxy derivatives of alkanes (substitutive IUPAC nomenclature).
The longest chain is taken as the principal chain, and the alkoxy group is named as a substituent.
Rule 2. Functional nomenclature (IUPAC) names ethers as derivatives of two alkyl groups, ordered alphabetically, ending the name with the word ether.
Rule 3. Cyclic ethers are formed by substituting a -CH2- with an -O- in a cycle. The numbering starts at the oxygen, and they are named with the prefix oxa- followed by the name of the cycle.