Why we use apostrophe t when write appelles in french?

You're likely thinking of the word "l'appelle" in French. The apostrophe is used in this case because it's a contraction of "le" + "appelle".

Here's a breakdown:

* "le" is the masculine singular definite article in French (meaning "the").

* "appelle" is the third-person singular present tense form of the verb "appeler" (meaning "to call").

When these two words are used together, the "e" at the end of "le" is elided (dropped) and replaced with an apostrophe. This happens in French when a word ending in a vowel or a silent "e" is followed by a word starting with a vowel sound.

Therefore, "l'appelle" means "he/she calls" or "it calls".