Spanish Accent Marks on Letters: When and Why to Use Them

A Spanish accent mark goes on a vowel for one of two reasons: to show the stressed syllable when a word breaks the normal stress pattern, or to separate two words spelled the same, such as tú (you) and tu (your). The mark is always the acute accent (´), and Spanish calls it a tilde.

Once you know which syllable you stress, a handful of rules tell you whether to write the accent. This guide covers those rules as set out in the Real Academia Española's 2010 Ortografía. If you only need the letters themselves, go to Spanish letters with accent marks.

What the accent on Spanish letters is called

Spanish separates two ideas that English lumps together:

So "casa" has an acento on the first syllable but no tilde. "Canción" has both. The full list of mark names across languages is on our accent mark names page.

Step 1: Find the stressed syllable

Say the word out loud and listen for the loudest syllable. Then count back from the end of the word. Spanish names each word by where its stress falls, and each group has its own rule.

Step 2: Apply the rule for that group

The agudas and llanas rules are mirror images. Most Spanish words are llanas ending in a vowel, n or s, which is why most words have no written accent at all.

Two details catch learners out. A llana ending in s after another consonant does take the accent: bíceps, cómics. An aguda ending in a consonant cluster such as -ts does not: robots.

Plurals can gain or lose the accent

Adding a syllable shifts the word into a different group, so the accent can appear or disappear:

Adverbs ending in -mente

An adverb in -mente keeps the accent of its adjective and nothing else: rápido gives rápidamente, fácil gives fácilmente, but lento gives lentamente.

Step 3: Check for a hiatus

When a stressed i or u sits next to a, e or o, it always takes an accent, even if the rules above say otherwise. The accent shows that the two vowels are pronounced in separate syllables.

Examples: día, país, reír, oído, búho, Raúl, maíz. "Día" is a llana ending in a vowel and would normally have no accent, but the hiatus rule overrides that.

Two weak vowels together (ui, iu) do not trigger this rule: construir, jesuita, ruido.

One-syllable words and diacritical accents

Words of one syllable normally never take an accent: fue, fui, dio, vio, fe, ti, pie. The exception is the diacritical accent (tilde diacrítica), which separates pairs of words that are spelled the same but do different jobs.

Compare: "Tú tienes tu libro" (you have your book) and "Sí, lo hago si puedo" (yes, I do it if I can).

Question and exclamation words

These words take an accent when they ask or exclaim, in direct and indirect questions alike:

qué, quién, quiénes, cuál, cuáles, cómo, dónde, adónde, cuándo, cuánto, cuán.

• ¿Dónde vives? (direct question)
• No sé dónde vive. (indirect question, still accented)
• La casa donde vivo. (relative, no accent)
• ¡Qué frío! (exclamation)

The same logic separates por qué (why), porque (because), porqué (the reason, a noun) and por que (for which).

The diéresis on ü

The ü appears only in the groups güe and güi. Without the dots, the u in gue and gui is silent, as in guerra and guitarra. With the dots, you pronounce it: pingüino, vergüenza, cigüeña, lingüística, agüero.

The diéresis has nothing to do with stress, so a word can have both marks: pingüino has a stressed i but needs no tilde, while lingüístico has both. The same two dots do other jobs in German and French, as covered in umlaut and diaeresis letters.

What changed with the 2010 Ortografía

The RAE and the other Spanish language academies published a new Ortografía in 2010. These are the changes you still see corrected most often:

• Solo and the demonstratives este, ese, aquel (and their forms) are written without an accent. "Solo quiero esto" is correct. A 2023 RAE note allows the accent only where the writer sees real ambiguity, but no accent is the default.
• O between numbers no longer takes an accent: 3 o 4.
• Some words are now treated as one syllable for spelling, so they lose the accent: guion, truhan, fie, lio, crie, hui.

Capital letters keep the accent

The RAE is explicit: accents are written on capitals too. Write Álvaro, Ángela, ÉXITO and ÁFRICA. The old habit of leaving capitals bare came from typewriters and early printing, not from any spelling rule. Our page on capital letters with accent marks shows how to type them.

Common mistakes

Ready to write? How to type Spanish accents gives the shortcut for each letter on Windows, Mac, Word and phones.