Monophthong

A monophthong is a vowel whose quality remains constant throughout its pronunciation.

Examples

 * [i] in reed, fee, or east
 * (NB: monophthongs are becoming increasingly rare in many dialects of American English, so some speakers may not produce this vowel as a monophthong.)

Origin
From Greek mono-phthongos 'single-sound'.

Related terms

 * diphthong (a vowel whose quality changes once during its pronunciation)
 * triphthong (a vowel whose quality changes twice during its pronunciation)