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A spurious diphthong (or false diphthong) is an Ancient Greek vowel that is etymologically a long vowel but written exactly like a true diphthong ει, ου (ei, ou).[1]


A spurious diphthong has two origins: from compensatory lengthening of short ε, ο (e, o) after deletion of a consonant or contraction of two vowels:[2]

In general, spurious ει, ου contracts from ε, ο + ε, ο, ει, ου. The specific rules are more complex.

True diphthongs

By contrast, true diphthongs are e or o placed before i or u. Some come from e-grade of ablaut + i, or o-grade + u, co-existing beside forms with the other grade:


Early in the history of Greek, the diphthong versions of ει and ου were pronounced as [ei̯, ou̯], the long vowel versions as [eː, oː]. By the Classical period, the diphthong and long vowel had merged in pronunciation and were both pronounced as long monophthongs [eː, oː].

By the time of Koine Greek, ει and ου had shifted to [iː, uː]. (The shift of a Greek vowel to i is called iotacism.) In Modern Greek, distinctive vowel length has been lost, and all vowels are pronounced short: [i, u].

Other dialects

Long e and o existed in two forms in Attic-Ionic: ει, ου and η, ω (ē, ō). In earlier Severer[7] Doric, by contrast, only η, ω counted as a long vowel, and it was the vowel of contraction.[8] In later forms of Doric, it contracted to ει, ου. Throughout the history of Doric, compensatory lengthening resulted in η, ω.[9]

"Severe" refers to the sterner-sounding open pronunciation of η, ω [ɛː, ɔː], in contrast to the closer ει, ου [eː, oː].


  1. ^ Smyth. A Greek grammar for colleges. § 25: diphthongs.
  2. ^ Smyth. A Greek grammar for colleges. § 6: genuine and spurious ei, ou.
  3. ^ Smyth. A Greek grammar for colleges. § 113: τι̯, θι̯ → σ(σ).
  4. ^ Smyth. A Greek grammar for colleges. § 221: -ya in short-a feminine.
  5. ^ ἔρχομαι. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
  6. ^ Smyth. A Greek grammar for colleges. § 36: vowel-grades.
  7. ^ Herbert Weir, Smyth. "INTRODUCTION:N3". A Greek grammar for colleges. The sub-dialects of Laconia, Crete, and Southern Italy, and of their several colonies, are often called Severer (or Old) Doric; the others are called Milder (or New) Doric. Severer Doric has η and ω where Milder Doric has ει and ου.
  8. ^ Smyth. A Greek grammar for colleges. § 59.5: Severer Doric εε → η; οο, εο → ω.
  9. ^ Smyth. A Greek grammar for colleges. § 37.2: Doric compensatory lengthening.