diphthong rule

Rule Core

The /aʊ/ diphthong is a common English vowel sound typically spelled ou or ow. It features a smooth glide from an open vowel to a rounded one within a single syllable. In stressed syllables, this pattern is highly consistent, as seen in bounce, cloud, cloudy.

Articulation Guide

Begin with the jaw relaxed and mouth open, tongue low and central. Glide smoothly as the lips round and the back of the tongue rises slightly. Airflow must remain continuous; do not split the sound into two separate vowels.

Word Analysis

• bounce: ou spells /aʊ/; final e is silent but preserves vowel quality.
• cloud: ou between consonants produces a clear /aʊ/.
• cloudy: the base cloud keeps /aʊ/ despite the suffix -y.

Pitfalls

Do not confuse /aʊ/ with other ou sounds such as /ʌ/ (young) or /uː/ (group). Avoid reducing it to a flat /a/ or /o/, which causes meaning errors.