Open vocal-tract sounds form the nuclei of most syllables. A vowel is a speech sound produced without significant obstruction of airflow, shaped by tongue height, tongue backness, and lip rounding.

Vowel inventories range from small sets to large systems with length, nasalization, or tone interactions. Acoustic analysis focuses on formant frequencies that correspond to vowel quality. Languages differ in how many vowel contrasts they maintain.

Vowel reduction in unstressed syllables shapes rhythm in languages like English. Teaching pronunciation often begins with vowel charts. Historical sound change frequently targets vowels, driving major shifts in lexical form over time.

• Speech sound with open airflow
• Described by height, backness, and rounding
• Usually forms the syllable nucleus
• Inventory size varies across languages