derived from arenes
by 1,2-addition of an oxygen atom to a formal double bond, e.g. 5,6-epoxycyclohexa-1,3-diene.
(Common usage has extended the term to include examples with the epoxy group bridging
PAC, 1995, 67, 1307
(Glossary of class names of organic compounds and reactivity intermediates based on
structure (IUPAC Recommendations 1995))
on page 1318