I am writing a short text involving the notion of "Eulerian path".
My problem is that I'm not sure about the pronunciation of the word "Eulerian", so I don't know whether I should write "a Eulerian path" (in case it sounds like "you-lerian") or "an Eulerian path" (in case it sounds like "oi-lerian").
After some research, it seems that the correct English pronunciation for "Euler" is "oiler" (source: OED). However, my version of the OED does not seem to have an entry for "Eulerian". A few people over the internet seem to claim that OED states that "Eulerian" is pronounced "you-lerian" although "Euler" sounds like "oiler". A few other people claim that "Eulerian" should be pronounced "oilerian".
So, what is the correct pronunciation?
NB I know "eu" is pronounced "oi" in German, but I'm interested in the English pronunciation of the word "Eulerian" (each language has its own conventions about words derived from foreign names).
Best Answer
The OED does indeed provide the pronunciation "/juːˈlɪərɪən/" for Eulerian, but a note at the side warns that "This entry has not yet been fully updated (first published 1891)". And the OED is just one source, anyway (even though it is certainly a very respectable one), and its main focus is not pronunciation. I think the "correct" pronunciation will be a matter of opinion.
According to the "The Free Dictionary" entry for "Eulerian path", the McGraw-Hill Dictionary of Scientific & Technical Terms gives the pronunciation as "[ȯi′ler·ē·ən ′path]", which presumably would correspond to an IPA transcription like /ɔɪˈlɛriən/ for "Eulerian".
The Google Ngram Viewer shows more use of "an Eulerian":
English conventions for the pronunciation of -ian words
The conventions for how English pronunciation corresponds to English spelling are infamously messy, and this contributes to uncertainties about the pronunciation of uncommon words like this that mostly appear in writing.
There are certain changes in pronunciation that tend to occur when we add the suffix -ian to a name (most consistently, a shift of the stress to the syllable directly before the suffix; it's also fairly common for the quality of the vowel in this syllable to change), but there is no general principle that says that adding -ian to a person's name requires us to adjust the pronunciation of the entire name to conform to typical English spelling-to-pronunciation patterns. For example, the first syllable of the word "Wagnerian" is often pronounced atypically for English: the OED ("This entry has not yet been fully updated (first published 1921)") gives "Brit. /vɑːɡˈnɪərɪən/, U.S. /vɑɡˈnɛriən/". (Despite what the OED says, I am an American and I would use the "r-controlled long e" sound, not the "short e" sound in the stressed syllable of "Wagnerian".)