In Spanish, unlike in English, adjectives must agree in both gender and number with the nouns they modify. For example, in English the adjective "red" remains the same in the phrases "one red shoe", "two red shoes", "one red shirt" and "two red shirts". Compare the Spanish equivalents of these phrases:
This remains true even when the adjective is separated from the noun, sometimes in another sentence:
Estas camisas de seda son exquisitas. El único problema es que salen muy caras.
Most Spanish adjectives, like rojo, caro, and exquisito, have four different forms: masculine singular and plural and feminine singular and plural. However, some adjectives have plural forms, but not different masculine and feminine forms. One example is azul:
Other adjectives with the same form in both masculine and feminine include verde, gris, marrón, inteligente, interesante, fácil, difícil, útil. As you can see, many adjectives of this type end in -l or -e.
Most adjectives have the same form whether they go before or after the noun that they modify, like exquisitas: exquistas camisas / camisas exquisitas. However, there are a few adjectives that have different forms when they are used before nouns. Many of the most commonly used adjectives in Spanish, such as bueno, malo, and grande, fall into this category, so it is important to be aware of this. The other tricky thing about these adjectives is that for some of them, the form only changes in the masculine! The examples below should illustrate all of the different forms: