sion=/ʒən/

Rule Core

-sion → /ʒən/ typically appears at the end of multisyllabic words, often from Latin -sio. When s occurs between vowels and follows a stressed syllable, /s/ becomes voiced, merging with -ion as /ʒən/ (e.g., vision, decision).

Articulation Guide

/ʒ/ is a voiced postalveolar fricative: the tongue approaches just behind the alveolar ridge without touching; air flows with friction while the vocal cords vibrate, then glides into a reduced /ən/.

Word Analysis

In vision /ˈvɪʒən/, -sion shows classic voicing. Compare sugar /ˈʃʊɡər/: although s + vowel also triggers change, it yields voiceless /ʃ/, clarifying the /ʒ/ vs /ʃ/ contrast.

Pitfalls

Do not read -sion mechanically as /ʃən/ or /sən/; voicing depends on stress and etymology.