Oesophagus is the British spelling of what American English writes as esophagus, and the oe is a Greek diphthong that came through Latin and never quite settled in English. The same digraph appears in amoeba and, with its partner ae, in aesthetic and haemorrhage.
American spelling has systematically simplified these to a plain e — esophagus, ameba, esthetic, hemorrhage — following Noah Webster's principle that spelling should record pronunciation rather than ancestry. British spelling kept the classical digraphs. Neither is more correct; they are two different answers to the same question, which is whether a word's spelling should tell you where it came from or how to say it. English has never decided, which is why the guide's cues work at all and also why they so often fail.
oesophagus (n.) alternative spelling of esophagus . See oe . Related: Oesophageal .
oesophagus came in through Greek, and its spelling follows that family's conventions.
How that family writes these sounds
| /iː/ or /ɛ/ in an old learned word | ae or oe — American spelling simplifies both to eaesthetic, amoeba, oesophagus |
What gives it away on the page
| ae, oe | Greek diphthongs through Latin. American spelling often simplifies them to e.aesthetic, amoeba, oesophagus |