Adverbs modify verbs, adjectives and other adverbs. Unlike adjectives and verbs, they are invariable in form, never changing in ending to agree with other elements in number, gender or person.

A large group of adverbs are derived from adjectives, adding a common ending. Others are similar or identical to the corresponding adjective.

Adverbs Ending in -mente

These adverbs are formed by adding the ending -mente to the feminine form of -o1 adjectives, and to the singular form of others2. This corresponds to the English adverbial ending -ly (skillfully, rapidly, etc.) Where applicable, original written accent is maintained3.

      1. claro→clara→claramente1; rápido→rápida→rápidamente1, 3
      2. inteligente→inteligentemente2; leal→lealmente2

When two or more -mente adverbs occur, the ending is dropped from all but the last:

      • Se terminó el proyecto rápida y exitosamente.
        • The project was completed quickly and successfully.

Not all adjectives take the -mente ending; some that do not include:

      • difícil
      • adjectives describing colors (negro, blanco, etc.)
      • those describing physical traits (feo, gordo, etc.)
      • adjectives of nationality (italiano, mexicano, etc.)
Distinguishing Adverbs and Adjectives

It is important to distinguish contexts in which an adverbial modifier is called for and those in which an adjective is required. Adjectives1 show agreement, but adverbs2 do not; examples:

  • Joaquín y Elena tienen mucha1 energía. Trabajan mucho2.
    • Joaquín and Elena have a lot of energy. They work a lot.
  • Admito que soy un alumno perezoso. Hay pocas1 personas que estudian tan poco2 como yo.
    • I admit that I'm a lazy student. There are few persons that study as little as I do.
  • Estoy medio2 dormido. Quiero descansar por media1 hora.
    • I'm half asleep. I want to rest for half an hour.
  • Pedro, tú comes demasiado2. Consumes demasiada1 comida.
    • Pedro, you eat too mucho. You consume too much food.
  • Ellas son las mejores1 (peores1) jugadoras del equipo. Juegan mejor2 (peor2) que yo.*
    • They are the best (worst) players on the team. They play better (worse) than I do.

    *More on irregular comparative forms.

Muy and mucho

Muy (very) functions only as an adverb; mucho can be either an adjective or an adverb (see examples above). They are not interchangeable, and are at times confused in some common contexts:

  • Mucho, and not muy, is used as a modifier in weather expresssions, because these involve a following noun*, not an adjective:
    • Hace mucho calor* (frío*) aquí en agosto. (Lit., It makes much heat, cold...)
  • Mucho is used rather than muy when the modified element* is omitted:
    • Pedro es muy listo*, ¿no? Sí, mucho.
      • Pedro is very smart, isn't he? Yes, very.