“Design,” “reason,” “music,” “because.” — All spelled with S. All pronounced with Z. In English, the letter S lies to you about half the time.
At the Foundation level, you learned S and Z differ by voicing. At the Everyday level, you learned the -s ending rule. Now let’s tackle the position where S/Z confusion causes the most problems: inside words.
Here’s the uncomfortable truth: in English, the letter S is pronounced as /z/ in hundreds of common words. There’s no single rule that covers all of them — but there are strong patterns.
The letter S is pronounced /z/ when it appears between two vowels.
This covers the majority of cases.
S between vowels = usually /z/:
design /dɪˈzaɪn/ · reason /ˈriː.zən/ · music /ˈmjuː.zɪk/
present /ˈprez.ənt/ · visit /ˈvɪz.ɪt/ · busy /ˈbɪz.i/
easy /ˈiː.zi/ · nose /noʊz/ · close (verb) /kloʊz/
because /bɪˈkɒz/ · please /pliːz/ · choose /tʃuːz/
But there are exceptions — S between vowels that stays /s/:
S between vowels = still /s/ (exceptions):
basic /ˈbeɪ.sɪk/ · house (noun) /haʊs/ · loose /luːs/
crisis /ˈkraɪ.sɪs/ · basis /ˈbeɪ.sɪs/ · promise /ˈprɒm.ɪs/
And here’s a beautiful pattern that connects to Week 2 (Word Stress):
Some words change S→Z when they change from noun/adjective to verb:
close
Adjective: “That was a close call.” /kloʊs/ (S)
Verb: “Please close the door.” /kloʊz/ (Z)
use
Noun: “What’s the use?” /juːs/ (S)
Verb: “Can I use this?” /juːz/ (Z)
house
Noun: “a nice house” /haʊs/ (S)
Verb: “to house refugees” /haʊz/ (Z)
excuse
Noun: “That’s no excuse.” /ɪkˈskjuːs/ (S)
Verb: “Excuse me.” /ɪkˈskjuːz/ (Z)
This pattern — noun/adjective with /s/, verb with /z/ — mirrors the stress shift pattern from Week 2 (REcord vs reCORD). English loves to distinguish word classes through subtle sound changes.
Now let’s complete the picture with the full voiced/voiceless fricative system:
The complete fricative pairs (same mouth, different voicing):
S /s/ ↔ Z /z/ — tongue near ridge (this week)
F /f/ ↔ V /v/ — teeth on lip (Week 6 + 12)
TH /θ/ ↔ TH /ð/ — tongue between teeth (Week 5)
SH /ʃ/ ↔ ZH /ʒ/ — tongue further back (vision, measure)
Every pair: same position, different voicing. One system, four locations.
✅ S or Z?
“Please close the door and use the design.”
→ pleaze · cloze · uze · dezign — ALL /z/! 🐝
Whenever you see S between two vowels in an English word, default to Z in your head.
You’ll be right more often than not. And when you’re wrong, it still sounds better than always using S. 🎯