When do you pronounce the s at end of a word that is before beginning with vowel in French?

In French, the final "s" of a word is almost always silent when followed by a word starting with a vowel.

Here are some examples:

* Le bus (the bus) - The "s" in "bus" is silent because the next word "le" starts with a vowel.

* Les amis (the friends) - The "s" in "amis" is silent because the next word "les" starts with a vowel.

However, there are some exceptions:

* Before a word starting with a vowel that represents a liaison:

* "Les enfants" (the children) - The "s" in "les" is pronounced because it creates a liaison with the following "e" in "enfants".

* In formal speech, the final "s" can be pronounced in some cases to distinguish between singular and plural forms:

* "Un ami" (one friend) vs. "Des amis" (some friends) - In formal speech, the "s" in "amis" might be pronounced in the plural form.

In general, the "s" at the end of a word before a vowel is usually silent, but there are some exceptions that depend on the specific context and level of formality.