Diphthongize

Part of speech: verb

Definitions

1. To change a single vowel sound into a two-part vowel sound, or to cause such a change to occur
2. To transform a pure vowel into a gliding vowel sound by adding a second vowel quality, or to undergo this transformation
3. To pronounce a vowel as a diphthong by combining it with a second vowel element, or to shift toward such a pronunciation

Etymology: "Diphthongize" is a plain technical formation: "diphthong" joined to the verb-forming suffix "-ize". A diphthong is a vowel sound that glides from one quality to another within a single syllable, as in the vowel of "boy" or "cow". The word is built from the Greek "diphthongos," which combined "di-," meaning "two," with "phthongos," meaning "sound" or "voice," so a diphthong is literally a "two-sound" vowel. The suffix "-ize" comes through Latin "-izare" from Greek "-izein," and it turns a noun into a verb meaning to make or to cause to become something. Adding it to "diphthong" yields a verb meaning to turn a single vowel into a diphthong, or to pronounce a vowel as a glide between two sounds. Phoneticians use it when describing sound changes, such as the historical shift in which English long vowels became diphthongs in the Great Vowel Shift.