Adjectives agree in both number (singular/plural) and gender (masculine/feminine) with the noun or pronoun they modify.
For regular adjectives the masculine form is the base form to which endings are added.
In most cases, the feminine adjective is formed by adding an e. The plural adjective is formed by adding s. Listen to the recorded examples to hear the pronunciation of the different adjective forms:
masculine singular: petit
feminine singular: petite
masculine plural: petits
feminine plural: petites
Note how the singular and plural forms of the masculine adjective sound the same, and the singular and plural forms of the feminine adjective also sound the same.
The adjective takes the masculine plural when the nouns it modifies are of different genders: Tammy et Rex sont petits. (Tammy and Rex are little.)
Irregular adjectives do not follow the rules given above.
In French, most adjectives follow the noun. (In English, adjectives come before the noun).