Relatives pronouns occur at the head of adjective clauses. They can refer to persons or things (physical objects, ideas, etc.) and to clauses. They are variously translated that, that which, which, who(m).

The clause headed by a relative pronoun may or may not be set off from the rest of the sentence by commas. Read about this before continuing.

Omission: Relatives are frequently omitted in English, but not in Spanish:

A teacher (that) I know speaks Japanese.→Una profesora que yo conozco habla japonés.

The noun or clause to which a relative pronoun refers is its antecedent; some examples in English:

• The book that you want to borrow is not available.
• The students with whom I spoke did well on the test.
• John drives too fast, which makes his wife nervous.

Below the most commonly used relative pronouns are presented, with examples.

The pronoun que is by far the most common relative pronoun. It can refer to persons or things; it is invariable, showing no agreement with its antecedent. It is very frequently the only relative pronoun that can be used when no comma or preposition is present, and is sometimes used in the presence of a comma or certain common prepositions.

• Tengo una amiga que* habla tres lenguas.
  • I have a friend who speaks three languages.
• Hay tres platos en el menú que son para vegetarianos.
  • There are three dishes on the menu that are for vegetarians.

*One should avoid the common error of using quien here.

Que appears mostly in non-comma clauses. In informal styles, it appears in comma-clauses as well:

El libro, que¹ me gusta mucho, es muy popular. El autor, que² es de mi país, se llama Gómez.

In more formal styles, el que^{1, 2}, el cual^{1, 2} or quien² is preferred. (See below)

After prepositions
Que is generally used after prepositions con, de and en when referring to things or persons, and after a when referring to things:

• ¿Cómo se llama la chica con que estuidias?
• Los países en que ellos viven son pobres.
• El tema de que hablamos es importante.
• ¿Dónde está la escuela a que ella va?

El que and el cual show number and gender agreement with the antecedent by use of the accompanying article form (el, la, los, las), with cual also having a plural form cuales. They can refer to persons or things. They are often interchangeable with each other and, when referring to persons, with quien. El que is the less formal and more common of the two.

Quien refers only to persons; it has a plural form quienes. It is not used with the article, and so shows no agreement in gender.

These are used in comma clauses and after prepositions:

• El coche, el que / el cual no marcha, es rojo.
  • The car, which doesn't run, is red.
• Las tiendas en las que / las cuales ellas trabajan están cerca (avoid common error!).
  • The stores that they work in are close by.
• Las empleadas con quienes / las que / las cuales yo trabajo son amables (avoid common error!).
  • The employees that I work with are nice.

Since they show agreement in gender, el que / el cual are sometimes to be preferred over quien:

Los novios de mis hermanas, los que (= novios) se llaman Pedro y Jaime, cenan con nosotros hoy.

El cual is preferable to el que after prepositions of more than one syllable and some lengthy prepositional phrases:

• Son las cajas dentro del cual guarda toda su ropa.
  • They are the boxes in which he keeps all his clothes.
• Todos los profesores, a algunos de los cuales no conozco bien, vienen a mi casa el viernes.
  • All the professores, some of which I don't know well, are coming to my house on Friday.

These invariable relatives refer to whole clauses, and so show no agreement in number and gender. The clause in question is always a comma clause.

• Nadie quiere ayudarme, lo que / lo cual me irrita.
  • Nobody wants to help me, which irritates me.
• Ese empleado nunca llega a tiempo, por lo cual fue despedido.
  • That employee never arrives on time, for which reason he was fired.

Donde can also function as a relative; examples:

• La casa donde él vive está lejos de la escuela.
  • The house where he lives is far from the school.
• Esa es la mochila de donde la alumna sacó los libros.
  • That's the backpack from which the student took out the books.