If you’ve ever listened to a news anchor from Madrid or watched a movie dubbed in Castilian Spanish, you’ve probably noticed it: the distinct, soft “th” sound for letters ‘c’ and ‘z’. Many English speakers hear this and jump to a simple conclusion: “That person has a lisp”. But what sounds like a speech impediment is actually one of the most defining and fascinating features of the Spanish language—a standard, not a mistake.

This pronunciation, known as distinción, is the linguistic ghost of a centuries-old sound shift. It’s the story of how one language, spoken in one small kingdom, evolved in different directions, creating a major phonetic divide that separates Spain from most of Latin America. Welcome to the world of seseo, ceceo, and the so-called “lisp that isn’t a lisp”.

The Three Sounds of Spanish ‘S’

Before we travel back in time, let’s get a handle on the three main pronunciation systems for the letters ‘s’, ‘c’ (before ‘e’ or ‘i’), and ‘z’. In modern Spanish, these letters represent the historical “sibilant” or hissing sounds.

1. La Distinción (The Distinction)

This is the standard pronunciation in most of northern and central Spain, including the capital, Madrid. It’s what non-Spaniards often mislabel as a lisp. In this system, two distinct sounds are maintained:

• The letter ‘s’ is pronounced as an /s/ sound, just like the ‘s’ in the English word “soup”. Example: siento (I feel).
• The letter ‘z’ (anywhere) and the letter ‘c’ (before ‘e’ or ‘i’) are pronounced as a voiceless interdental fricative, or /θ/. This is the “th” sound in the English word “think”. Example: ciento (one hundred).

So, for a speaker with distinción, casa (house) and caza (hunt) are two completely different-sounding words: “kasa” vs. “katha”.

2. El Seseo

This is by far the most widespread pronunciation system in the Spanish-speaking world. It is the standard throughout all of Latin America, the Canary Islands, and large parts of southern Spain (Andalusia). In seseo, there is no distinction.

• The letters ‘s’, ‘z’, and ‘c’ (before ‘e’ or ‘i’) are all pronounced as an /s/ sound.

For a seseo speaker, casa and caza are homophones—both are pronounced “kasa”. The same goes for cocer (to cook) and coser (to sew). Context is king here.

3. El Ceceo

This is the rarest of the three systems, found primarily in certain rural areas of southern Spain, particularly in parts of Andalusia like Cádiz. It’s the mirror image of seseo.

• The letters ‘s’, ‘z’, and ‘c’ (before ‘e’ or ‘i’) are all pronounced as the /θ/ (“th”) sound.

A ceceo speaker would pronounce the phrase “gracias por su servicio” (thank you for your service) as something like “grathias por thu therbithio”. While perfectly logical from a linguistic standpoint, ceceo is often socially stigmatized in Spain and viewed as a rustic or uneducated pronunciation, a prejudice that has no basis in linguistic validity.

A Trip Back in Time: The Medieval Sound Shift

So, how did this split happen? The answer lies in the rich and complex sound system of Medieval Spanish. Around the 15th century, Old Spanish didn’t just have one or two hissing sounds; it had a whole set of them, which linguists call sibilants. These were:

• /s/ – A sharp ‘s’ sound (like in “sea”), spelled with ‘ss’ between vowels.
• /z/ – A buzzy ‘z’ sound (like in “rose”), spelled with ‘s’ between vowels.
• /ts/ – A sound like the “ts” in “cats”, spelled with a ‘ç’ (c-cedilla).
• /dz/ – A sound like the “ds” in “ads”, spelled with a ‘z’.

During the 15th and 16th centuries, the Spanish language underwent a massive simplification of these sounds. However, this simplification took two different paths depending on the region.

Path 1: Northern and Central Spain

In the north, the heartland of Castile, the system simplified but kept a distinction. First, the voicing disappeared, meaning the buzzy /z/ and /dz/ sounds became the voiceless /s/ and /ts/. Now they had just two sounds: /s/ and /ts/.

To keep them from sounding too similar, a crucial shift occurred. The dental sound /ts/ (from the old ‘ç’ and ‘z’) moved forward in the mouth. The tongue went from touching the back of the teeth to resting between the teeth. This created the new interdental sound: /θ/ (“th”). The other sound, /s/, remained more or less the same.

The result? Distinción.

caza (from old caça, /katsa/) became /kaθa/.

casa (from old cassa, /kasa/) stayed /kasa/.

Path 2: Southern Spain and the Americas

In the south (Andalusia), the simplification process went a step further. The two sounds, /ts/ and /s/, didn’t just shift to stay separate—they merged into one.

In most of the influential southern cities like Seville and in the Canary Islands, they both collapsed into the /s/ sound. This is seseo. Since Seville and the Canary Islands were the primary gateways for colonization and trade with the Americas, this was the pronunciation that crossed the Atlantic and became the standard for an entire continent.

In other, more isolated parts of the south, both sounds happened to merge into the /θ/ sound instead. This gave rise to ceceo.

So, Who Is “Correct”?

This is the easiest question to answer: everyone.

Distinción is the prescriptive standard of pronunciation in Spain. Seseo is the prescriptive standard in all of Latin America. Neither is better, more correct, or more ancient than the other. They are simply different, equally valid outcomes of the same historical process. To claim that Latin Americans “can’t pronounce the z” is as absurd as claiming that Americans “can’t pronounce the ‘r’ at the end of ‘car'” just because many British speakers don’t.

The existence of these systems adds a layer of richness to the Spanish language. It’s a constant, audible reminder of history—of medieval kingdoms, of voyages across the ocean, and of the beautiful, unpredictable way that language lives and breathes. So the next time you hear that “lisp” from Spain, you’ll know you’re not hearing an error, but an echo of the 16th century.