When does S sound like Z in French?

Updated: November 14, 2022 by Mylene in Pronunciation Lessons  ▪ English Français  

Have you ever wondered how to pronounce the letter S in French? The letter S has 2 pronunciations in the middle of a word and there are rules around this. In this article, you’ll learn how to pronounce the letter S between two vowels in French. You’ll also discover words that have similar spellings but different meanings. A single S or a double SS can change the meaning of a word!

In this post, you’ll learn:

• Pronunciation of the letter S in the middle of a word
• The right way to pronounce S (a video)
• Similar words but different meanings
• Pronunciation exceptions with the letter S

How to pronounce S in the middle of a word?

When the consonant S is between two vowels, the letter S is pronounced Z such as in “valise” and “oiseau”. To break the /z/ sound in French words, the rule is to add a double SS. 

For example, words like “tasse” or “classe” have a double SS and therefore are pronounced with the sound /s/ : 

• tasse is pronounced /tas/
• classe is pronounced /klas/

Of course, there are other cases where the letter S is pronounced as /z/.

Master Your French blog covers a wide range of topics related to French pronunciation, listening, culture, and much more. Among many articles, you can learn about French silent letters such as the silent h.

This article is about the specific case when the letter S is between two vowels. To learn more about this topic check the guide to Silent Letters in French.

Watch the right way to pronounce S in French

In the video below, I show you different examples where the consonant S is pronounced as /s/ and other examples where the letter S is pronounced as /z/.

In addition, discover similar words that have different meanings when having a single S or double S. This is how you’ll learn how to correctly pronounce the letter S in words like “poison” and “poisson”, “désert” and “dessert”.

Click to watch this video The Right Way To Pronounce S in French: 5 Similar Words But Different Meanings.

Be sure to watch the video to learn more about the pronunciation of the letter S. To follow more updates, subscribe to the YouTube channel. 

Similar words but different meanings

French words like “masque” and “chaussure” are pronounced with the oral consonant /s/ while other words such as “valise” and “vase” are pronounced with the oral consonant /z/ :

• masque is pronounced /mask/
• chaussure is pronounced /ʃosyr/
• valise is pronounced /valiz/
• vase is pronounced /vaz/ 

In the following, you’ll find a list of words that have similar spelling but their meaning is very different. In terms of spelling, every pair of words have one word with a single S and another word with a double SS.

Cousin vs. Coussin

The word cousin in French refers to a child of one’s uncle or aunt. It has the same meaning in English as in French. In addition, the pronunciation of the letter S in French is similar to how it is pronounced in English.

In the word “cousin”:

• the letter S is between two vowels, the U and the I
• the S in “cousin” is pronounced as a /z/ sound

In French, there is a word that has its spelling very similar to “cousin”. It is the word “coussin”. While both words share many common letters, their meaning is totally different. In fact, “coussin” means pillow. 

In terms of spelling, the difference between the word “coussin” and “cousin” is that:

• “coussin” is written with a double SS
• as a result, the word “coussin” is pronounced with an /s/ sound

Désert vs. Dessert

Another pair of words in French that have their spelling similar is “désert” and “dessert”. The word “désert” means the desert. As for “dessert” it means dessert in English.

Let’s take the sentence: “Je mange un dessert dans le désert” (I eat a dessert in the desert). You can spot the two words “dessert” and “désert ” in this sentence.

In terms of pronunciation, the S in the word “désert” is pronounced as a /z/ sound because the letter S is between two vowels (e).

On the other hand, “dessert” has a double SS which results in the phonetic sound /s/.

Ruse vs. Russe

The word “ruse” in French refers to cunning, a cunning fox. If we take the word “Russe”, which means Russian, it is clear that both words are similar in terms of spelling.

Here is one sentence that has both words: Ce Russe ruse (this cunning Russian). This is another situation where the letter S in “ruse” is between two vowels, the U and the E.

The word “Russe” has a double SS which means that the pronunciation of “Russe” is with the sound /s/. Of course, “ruse” is pronounced with the sound /z/.

Poison vs. Poisson

Let’s now take a well-known example with the words “poisson” and “poison”. While the word “poisson” means fish, the word “poison” also means poison in English.

The only difference between “poisson” and “poison” is that the former word has a double SS while the latter has a single S. As we saw in the previous example, whenever an S is between two vowels it must be pronounced as /z/. This is the case of “poison”. In order to make a /s/ sound, a word should have a double SS. It is the case of the word “poisson”. So be sure to write “poisson” with a double SS, otherwise, you’ll be referring to poison!

Lisent vs. Lissent

The last example in which a single s between two vowels is pronounced /z/ is the word “lisent”:

• The word “lisent” is the French verb “lire” (to read) conjugated to the present tense in plural.
• “Lisent” is very close in terms of spelling to “Lissent” which means to smooth in English.

Now, you know that “lisent” is pronounced with /z/ while “lissent” is pronounced with the sound /s/.

Pronunciation and exceptions with the letter S

There are some words that are written with a single S but are pronounced with the sound /s/. Let’s see some of these exceptions.

Exception 1: After the prefix “R”

The word “resaler” has a single S but this s is pronounced as /s/ (not as /z/). Resaler means to add more salt.

Other examples with the prefix “re“ :

• resalir is pronounced /rəsalir/ wich means to get dirty again
• resaluer is pronounced /rəsalɥe/ wich means to say hi again

Exception 2: After the prefix “A”

“Asymétrie” is pronounced with an /s/ regardless of having the letter S between two vowels. Asymmetry is the meaning of “asymétrie” in English.

Exception 3: After the prefix “Para”

After the prefix “para”, the letter S is pronounced as /s/ even if it is located between two vowels. Here is one example “parasol” (beach umbrella).

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