In Spanish, adjectives must match the nouns they describe. This means they need to agree in two main ways: gender and number. Here are some easy rules to remember:

1. Gender Agreement:

   • Masculine nouns usually end in “-o.” For example, "niño" means boy.
   • Feminine nouns often end in “-a.” For example, "niña" means girl.
   • Adjectives must match the noun’s gender:
     • For a boy: "El niño es inteligente." (The boy is smart.)
     • For a girl: "La niña es inteligente." (The girl is smart.)

2. Number Agreement:

   • For singular nouns, use the basic form of the adjective:
     • Singular: "El libro es interesante." (The book is interesting.)
   • For plural nouns, change the ending:
     • Typically, add “-s” if the word ends in a vowel. Add “-es” if it ends in a consonant:
       • Plural: "Los libros son interesantes." (The books are interesting.)
       • Feminine Plural: "Las niñas son inteligentes." (The girls are smart.)

3. Examples:

   • A masculine singular adjective: "perro negro" (black dog).
   • A feminine plural adjective: "gatas blancas" (white cats).

Always remember to change adjectives based on the gender and number of the nouns. This keeps everything correct!