Iota subscript

Diacritic mark in the Greek alphabet

The iota subscript is a diacritic mark in the Greek alphabet shaped like a small vertical stroke or miniature iota ⟨ι⟩ placed below the letter. It can occur with the vowel letters eta ⟨η⟩, omega ⟨ω⟩, and alpha ⟨α⟩. It represents the former presence of an offglide after the vowel, forming a so‐called "long diphthong". Such diphthongs —phonologically distinct from the corresponding normal or "short" diphthongs —were a feature of ancient Greek in the pre-classical and classical eras.

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