In French, adjectives must agree in number and gender with the noun they describe. To make an adjective feminine, an "e" is typically added to the end. However, some adjectives are irregular and their endings change, such as "if" becoming "ive". Adjectives also change endings to agree with plural nouns, such as "iers" becoming "ières". The document then provides examples of adjectives and identifies whether they are masculine or feminine, singular or plural forms.