¡Los acentos importan! — the subject is Panamanian politician Ricardo Martinelli. The accent on él is from rule 3 below, and the accent on cambió is from rule 2.

People are always asking me about Spanish accent marks. I don’t think this is because accents are intrinsically difficult, but rather that most explanations fail to put together some related issues. It’s a not-seeing-the-forest-for-the-trees situation.

As I mentioned in an earlier post, what unites all uses of Spanish accent marks is that they serve to highlight unusual stress: stress on an unusual vowel, syllable, or word.

1. A written accent can break the normal rules for which vowel to stress within in a vowel sequence. Spanish normally stresses the second of two vowels, as in fuE·go “fire” or diA·blo “devil” (this is actually a slight simplification). A written accent signals a deviation from this pattern, as in con·ti·nÚ·e “continue” or co·mÍ·a·mos “we were eating”. Notice that changing the stress pattern also creates an additional syllable. What power!
2. A written accent can break the normal rules for which syllable to stress within a word. Spanish normally stresses the last syllable of a word that ends in a consonant, and the next-to-last syllable of a word that ends in a vowel. Think mu.jEr vs. hOm.bre. With a written accent mark you can break this pattern: lÁ.piz ends in a consonant, and hin.dÚ and te.lÉ.fe.no both end in a vowel. A final s or n doesn’t “count” because it’s usually a grammatical marker: there’s no stress difference between hA.bla, hA.blas, and hA.blan, or between cu.ca.rA.cha and cu.ca.rA.chas.
3. A written accent marks the member of an otherwise identical word pair that usually carries more stress within a sentence, and can even stand alone. This is most obvious for question words. Compare the stress on accented versus unaccented quien and como in ¿Quién se llama Juan? and ¿Cómo nada un pez? versus Tu amigo, quien se llama Juan, nada como un pez. The accented varieties can stand alone: ¿Quién? ¿Cómo?

Once you know these fundamental rules, mysteries vanish. Why does más have an accent? To distinguish it from the obscure word mas, which means “but”; note that the accented version can stand on its own (¡Más!). Why do some words gain an accent in the plural, some lose an accent, and some keep an accent? These cases all have to do with final n or s:

• Words that gain an accent change from regular to irregular in the plural. Singular jO·ven has regular stress (next-to-last syllable, word ends in n) but plural jÓ·ve·nes is irregular (third-to-last syllable).
• Words that lose an accent change from irregular to regular in the plural. Singular ja·mÓn has irregular stress (final syllable, word ends in n) but plural ja·mO·nes is regular (next-to-last syllable, word ends in s).
• Words that keep an accent have irregular stress in both the singular and the plural. For ca·fÉ and ca·fÉs, regular stress would be on the a; for fÁ·cil and fÁ·ci·les, regular stress would be on the i.

Even native speakers make accent mark mistakes, so please — don’t stress! 😉