Choosing a Relative Pronoun

Spanish has seven common relative pronouns, and textbooks usually introduce them one page at a time. This page does the opposite: it gives you a single decision tree you can run through in your head whenever you're about to connect two clauses. By the time you finish reading, you should be able to look at any sentence and reach for the right word.

The quick answer

If you only remember one sentence from this page, remember this: que is the default. Unless something specific forces your hand — a preposition, a possessive, a place, a whole-clause antecedent — que is almost always correct. The decision tree below exists to tell you when to override that default.

Decision tree

Step 1 — Is there a preposition in front of the relative pronoun?

If no, skip to Step 3.

If yes, go to Step 2.

Step 2 — What does the relative refer to, and what preposition is it?

• People, after a short preposition (a, de, con, en, por, para): use preposition + quien (or preposition + el que in everyday speech). Both are heard; quien is a touch more formal.
• Things, after a short preposition: use preposition + el que / la que / los que / las que. The article agrees with the thing referred to.
• After a longer or compound preposition (detrás de, a través de, gracias a, según, durante, sin embargo de): use el cual / la cual / los cuales / las cuales. El que also works; que alone does not.
• For a place (after en, a, de meaning "where"): you can use donde instead of en el que. It's shorter and very common.

Step 3 — Does the relative refer to a whole idea, not a specific noun?

If the antecedent is a previous clause, a fact, or an abstract concept — not a countable thing — use lo que (or lo cual in more formal writing).

Step 4 — Are you expressing possession ("whose")?

Use cuyo / cuya / cuyos / cuyas. It agrees with the thing possessed, not with the possessor — the same rule as any adjective.

Note that cuyo is almost entirely a written-register word. In speech, Spanish speakers avoid it and restructure the sentence: El escritor que escribió la novela que ganó...

Step 5 — Is the clause non-restrictive (set off by commas)?

In defining clauses (no commas), just use que. In non-restrictive clauses — where the information is a side remark — que is still acceptable, but formal writing often prefers quien (for people) or el cual (for things).

Step 6 — Default

If none of the above applied, use que. This will cover the vast majority of sentences you'll ever write.

Examples — walking through the tree

Let's run the tree on ten sentences.

1. "The woman who lives next door is a doctor." No preposition, no whole-clause antecedent, no possession → default → que.

2. "The friend I went to the concert with is Mexican." Preposition con, refers to a person → con quien.

3. "The building behind which we parked is new." Compound preposition detrás de → el cual.

4. "He didn't call me, which worries me." Antecedent is the whole previous clause → lo que.

5. "The writer whose book I'm reading is from Colombia." Possession → cuyo, agreeing with libro (masculine singular).

6. "The park where we met is closed." Place → donde.

7. "My brother, who studies medicine, just turned 25." Non-restrictive, person → quien (formal) or que (neutral).

8. "The key with which he opened the door was rusty." Short preposition + thing → con la que.

Quick reference table

Common traps

• Don't drop the relative pronoun. English lets you say "the book I read," but Spanish must include que: el libro que leí.
• cuyo agrees with the thing possessed, not the owner. El niño cuyas madres... is wrong if you mean "the boy whose mothers" — wait, actually it's right, because madres is feminine plural. The lesson: look at the noun after cuyo, not before.
• donde is not just a question word. It doubles as a relative: la casa donde vivo. If you're talking about going to a place, adonde (or a donde) is more precise.
• que vs qué: the relative has no accent. The question word does. Completely different functions.

Takeaway

Out of all seven relative pronouns, only que and lo que come up constantly. The rest are triggered by three things: a preposition, a place, or a possessive. Memorize those three triggers, and the decision tree collapses to a single reflex — reach for que unless one of the triggers fires.