There are a bunch of Greek loanwords in English that orthographically include the vowel sequence 'ae'. Examples include:

The 'ae' vowel here is pronounced [i] in English, but at least according to those Wikipedia pages, it was pronounced [a͡ɪ] in the Greek these words were borrowed from.

How did this convention come about?

  • Were these words borrowed long enough ago that some vowel shift has happened in English since then?
  • Is the [a͡ɪ] pronunciation only true for ancient Greek, and the [i] reflects their pronunciation in modern Greek?
  • Something else?
  • 1
    The standard English pronunciation of "ae" is /i/, not only in Greek words, but also in Latin words/names like Caesar, larvae.
    – fdb
    Jun 5, 2021 at 12:10
  • 1
    In modern Greek this diphthong is pronounced /e/ (like the vowel in the word "set")
    – Thanassis
    Jun 14, 2021 at 23:19

2 Answers 2


Greek αι (/aj/) was regularly borrowed into Latin as ae (/aj/*).

In Latin, ae eventually monophthongized into /ɛː/; in Vulgar Latin/Proto-Romance, vowel length was lost and this eventually merged with /ɛ/ or /e/.

As a result, Modern French regularly renders Latin ae < AGrk αι with é /e/, as in éther < αἰθήρ as mentioned by Arnaud Fournet. (Old French often used ae, imitating the Latin, but the sound was likely the same.)

These words were then borrowed from French into English, and subjected to the Great Vowel Shift, which turned /eː/ into /iː/.

The end result is a tradition of spelling Ancient Greek αι as ae (Britain) or e (America**), and pronouncing it /iː/.

* The second element in the Latin diphthong was probably more open than the Greek one, hence the spelling. But I'm using broad transcriptions here.

** Thanks to Webster's spelling reforms.

  • These words are spelled with e in American English? I've seen "eon," but never "egis," and "ether" and "aether" are not alternate spellings for me, they're two different words. Are there other examples of this spelling convention? Regardless, solid answer and +1!
    – A_S00
    Jun 5, 2021 at 4:47
  • 6
    @A_S00 Many are; the ones with ae in American English are generally a deliberate archaicism. Consider arch(a)eology, encyclop(a)edia, p(a)edagogy, an(a)emia, f(a)eces…
    – Draconis
    Jun 5, 2021 at 4:54
  • Neat, those ones are so lexicalized for me I didn't even know most of them were Greek loanwords!
    – A_S00
    Jun 5, 2021 at 4:57
  • 3
    @A_S00 While ether and aether are nowadays more or less consistently kept apart, they come from the same word, and ether originated as just one meaning of aether, the Americanised spelling being used to lexicalise the distinction. Note how the Wikipedia disambiguation page includes all three spellings. (Also, while the other examples Draconis gave are indeed Greek words that were borrowed into Latin, faeces is a native Latin word, not a Greek one. But the vowel is treated the same regardless of whether it’s an original Latin <ae> or a Latinised Greek <αι>.) Jun 5, 2021 at 7:50
  • See also "caesar".
    – nick012000
    Jun 6, 2021 at 12:05

I think the vowel i: in present-day English comes from Middle English e: (the famous Great Vowel shift).
Middle English e: in aeon, aether, is probably based on French éon, éther, etc, which are a regular rendition of ai-.
The spelling ae is obviously a bit pedantic and directly taken from Greek.

  • 3
    Directly taken from Latin – as you say, Greek has <αι>, not <αε/ae>. In cases where the Greek source actually has <αε> (or <αη>), Latin would have /a.e/ (not /aɪ/), French would have <aé>, and the English pronunciation usually isn’t /iː/, cf. aero-. Jun 5, 2021 at 9:24

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