Seseo

Seseo is the name for a pronunciation feature that is absolutely universal in Latin America: the letters c (before e or i), s, and z are all pronounced with the same [s] sound. There is no [θ] ("th") sound in any variety of Latin American Spanish.

This one feature alone is enough to tell a Latin American accent from a Castilian one within the first few words.

The Basic Rule

In Latin American Spanish, all of the following are pronounced [s]:

• s — always
• z — always
• c before e or i — always

So casa, zapato, and cena all begin with the same consonant sound: [s].

In each of these sentences, a Latin American speaker pronounces every c, s, and z identically. A speaker from central or northern Spain would make three separate sounds: [s] for s, and [θ] for c (before e, i) and for z.

What "Distinción" Sounds Like

The Castilian system that Latin America doesn't use is called distinción — literally, "distinction." In distinción, [s] and [θ] are two separate phonemes, just like English [s] and [θ] in sink and think.

Distinción speakers (mostly in northern and central Spain) draw minimal pairs from the difference:

• casa [ˈkasa] ("house") vs. caza [ˈkaθa] ("hunt")
• cocer [koˈθer] ("to cook") vs. coser [koˈser] ("to sew")
• ves [bes] ("you see") vs. vez [beθ] ("time, occasion")

In Latin America, each of these pairs is a homophone. Context disambiguates them easily.

Both sentences sound completely different in meaning, of course, but the words casa and caza are pronounced identically by a Latin American speaker.

Spelling Consequences

Seseo creates a real spelling challenge: because s, c, and z all sound the same, children learning to read and write in Latin America cannot rely on pronunciation to decide which letter to use.

Many common words have to be memorized by spelling alone:

• hacer — not haser or hazer
• vez — not ves (though ves, "you see," is spelled differently because it's a different word)
• cocina — not cosina
• necesitar — not nesesitar

Spelling bees and dictados (dictation exercises) in Latin American schools put a lot of focus on distinguishing s, c, and z in writing.

Regional Variation Within Seseo

While all of Latin America is seseante, the quality of the [s] itself varies:

• Highland Mexico, Andes, Guatemala: a very crisp, clear [s].
• Caribbean, southern Argentina, Chile: weakened or aspirated [s] — it may be pronounced as [h] or dropped entirely, especially at the end of a syllable. Los niños may sound like loh niñoh or lo niño.

A speaker from highland Mexico will say every s clearly; a Caribbean speaker may pronounce it as Loh chicoh ehtán en la ehcuela.