"Ce," "cet," "cette," and "ces"

"Ce," "cet," "cette," and "ces" are all demonstrative determiners in French, used to indicate a specific noun in relation to the speaker. 

They agree in gender and number with the noun they modify.

Here's how to use them:

    "Ce" (masculine singular): Used before masculine singular nouns that start with a consonant sound.
        Example: Ce livre (This book)

    "Cet" (masculine singular): Used before masculine singular nouns that start with a vowel sound.
        Example: Cet arbre (This tree)

    "Cette" (feminine singular): Used before feminine singular nouns.
        Example: Cette maison (This house)

    "Ces" (plural, masculine or feminine): Used before plural nouns, regardless of gender.
        Example: Ces livres (These books)
        Example: Ces maisons (These houses)

Remember that agreement in gender and number is important. 

For example, you wouldn't say "cet maison" because "maison" is feminine; it would be "cette maison." Similarly, for plural nouns, you wouldn't say "ces livre" but "ces livres."

These determiners are essential in French for indicating proximity or specifying which noun you're referring to.