In American English, s can be pronounced either as /s/ or /z/. As easy as it may sound, in fact, you can be quite confused between the two. But don’t you worry, ELSA is here to offer some help.

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Be clear about the difference between /s/ and /z/

• The /s/ sound:  Relax your mouth a bit. Place the tip of your tongue close to the back of your teeth, but don’t touch them. Let the air out between your teeth to make a hissing sound.
• The /z/ sound: Place your tongue just like in the s position, but this time, tense your tongue a bit more when you push the air out. If you can feel some sort of vibration, you’ve done it correctly

Image: WikiHow

The 4 basic rules for /s/ and /z/

1. When “s” comes after a voiceless consonant, it is pronounced as /s/

Eg: books, cats, stops,…

2. When “s” comes after a voiced consonant or a vowel, it is pronounced as /z/

Eg: feels, eggs, lives,…

3. Double “s” is pronounced as /s/

Eg: success, less, lesson,…

4. For words that require you to add an “e” before adding “s”, you should pronounce “s” as /s/

Eg: churches, dishes, matches,…

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This may sound so small a point that you think you can master it after practicing a few times. However, some native speakers don’t even recognize these differences when they speak the s sound. That’s why if you ever ask them how to pronounce s in feels, they would probably just tell you to say it as /s/.

If you listen carefully enough, your awareness can be built gradually. Yet it’s always better to learn the rules, right?

Good luck!

Source: speakmethod.com