If you’ve ever studied a Romance language, you’ve probably encountered a perplexing puzzle. You learn that Latin is the mother tongue, the great ancestor from which French, Spanish, Italian, Portuguese, and Romanian all spring. You see the clear family resemblance in words like pater (father) or flos (flower). And then you hit a wall.

How on earth does the Latin word centum, pronounced ‘kentum’ (like the first part of “Kentucky”), become the Italian cento (‘chento’), the French cent (‘sahn’), and the Spanish ciento (‘thiento’)? How did one hard ‘k’ sound shatter into such a diverse array of sounds—’ch’, ‘s’, and ‘th’?

The answer is not random chaos. It’s one of the most fascinating and far-reaching sound changes in linguistic history: palatalization. This “Great Consonant Shift” is arguably the single biggest reason for the dramatic phonetic differences we hear among the major Romance languages today.

The Starting Point: Classical Latin’s Hard ‘K’ and ‘G’

To understand the change, we have to know what we’re starting with. In Classical Latin, the letter ‘C’ was always pronounced as a hard ‘k’ sound, no matter what vowel came after it. The letter ‘G’ was also always hard, like the ‘g’ in “go”.

• CENTUM (one hundred) was pronounced ‘kentum’.
• CIVITAS (city/state) was pronounced ‘kiwitas’.
• GELU (frost) was pronounced ‘gelu’ (with a hard ‘g’).
• GENTEM (people/clan) was pronounced ‘gentem’ (with a hard ‘g’).

For centuries, this was the standard. But as the Roman Empire fragmented, the way Vulgar Latin (the spoken language of the common people) was pronounced began to drift. And the key catalyst for this change was the tongue’s position in the mouth.

What is Palatalization, Anyway?

In simple terms, palatalization is a sound change where a consonant’s point of articulation shifts closer to the hard palate (the roof of your mouth). It’s a form of assimilation, where a sound becomes more like a neighboring sound.

Try this yourself: Say the words “coo” and then “key”.

When you say “coo”, your tongue is pulled back to make the ‘k’ sound before the back vowel ‘oo’. When you say “key”, your tongue is pushed forward and high up against your hard palate to anticipate the front vowel ‘ee’. That ‘k’ in “key” is already slightly palatalized.

In Vulgar Latin, this natural process went into overdrive. The “culprits” that triggered this change were the front vowels ‘e’ and ‘i’, and the semivowel ‘y’ (known to linguists as a ‘yod’ sound). When a ‘k’ or ‘g’ sound came before one of these “palatalizing” vowels, it began to get “pulled” forward, starting a chain reaction that played out differently across the former empire.

The Great Divergence: Following the ‘K’ Sound

Think of palatalization as a multi-stage process. The fascinating part is that different language groups stopped the process at different stages, like getting off a train at different stations.

Stage 1: The Italian & Romanian Path (Affrication)

In the regions that would become Italy and Romania, the palatalized ‘k’ sound developed into an affricate—a sound that starts as a stop and releases as a fricative. Specifically, it became the ‘ch’ sound we hear in “church”, phonetically written as /tʃ/.

• Latin CENTUM (‘kentum’) → Italian cento (‘chento’)
• Latin CAELUM (‘kailum’) → Italian cielo (‘chelo’)
• Latin PACEM (‘pakem’) → Italian pace (‘pachey’)

The hard ‘g’ sound followed a similar path, becoming the ‘j’ sound in “judge”, written as /dʒ/.

• Latin GENTEM (‘gentem’) → Italian gente (‘jente’)

This path is relatively straightforward: k → tʃ. They got off at the first major stop.

Stage 2: The French Path (Sibilization)

Old French started on the same path as Italian, turning ‘k’ before ‘e’ and ‘i’ into /tʃ/. We can see this in early texts. But it didn’t stop there. Over time, this /tʃ/ sound was simplified by dropping the initial ‘t’ stop, leaving only the ‘sh’ part, which then further simplified to an ‘s’ sound (/s/).

The process looked like this: k → tʃ → s.

• Latin CENTUM (‘kentum’) → Old French tʃent → Modern French cent (‘sahn’ – the ‘t’ is silent)
• Latin CIVITAS (‘kiwitas’) → French cité (‘see-tay’)

This explains the soft ‘c’ in French. The ‘g’ sound also went one step further than in Italian: g → dʒ → ʒ (the ‘zh’ sound in “measure”).

• Latin GENTEM (‘gentem’) → French gens (‘zhahn’)

Stage 3: The Spanish Path (Further Forwarding)

Spanish also took the change further, but in a different direction. The original ‘k’ sound first became an affricate, but a different one: /ts/ (like the end of “cats”).

k → ts

Then, in Castilian Spanish, this /ts/ sound moved even further forward in the mouth, becoming the interdental fricative /θ/—the ‘th’ sound in “think”.

k → ts → θ

• Latin CENTUM (‘kentum’) → Old Spanish tsiento → Castilian Spanish ciento (‘thiento’)
• Latin CIVITAS (‘kiwitas’) → Spanish ciudad (‘thyoo-dahd’)

Interestingly, in Latin America and southern Spain, the evolution stopped at a different final stage. The /ts/ sound simplified to /s/, just like in French, but arriving there from a different intermediate step. This is why ciento is pronounced ‘siento’ in most of the Spanish-speaking world.

The ‘g’ sound in Spanish took an even wilder turn, eventually becoming the velar fricative /x/, the harsh, throaty ‘j’ sound in Spanish.

• Latin GENTEM (‘gentem’) → Spanish gente (‘khente’)

The Sounds That Escaped: When Palatalization Didn’t Happen

This whole process begs the question: what about words like Italian and Spanish casa (house) or cantare (to sing)? Why do they still have a hard ‘k’ sound?

The answer lies in the rule: palatalization was only triggered by front vowels ‘e’ and ‘i’. When the ‘k’ or ‘g’ sound was followed by the back vowels ‘a’, ‘o’, or ‘u’, nothing happened. The sound remained stable and hard.

• CASA (house) → Italian/Spanish casa (hard ‘k’)
• CANTUS (song) → Italian/Spanish canto, French chant (Here, a *different* palatalization before ‘a’ happened in French, creating the ‘sh’ sound!)
• CORONA (crown) → Italian/Spanish corona, French couronne (hard ‘k’)

And then there’s Sardinian, the linguistic rebel. Spoken on the island of Sardinia, it’s often considered the most conservative Romance language, having resisted many of the sound changes that swept the mainland. In Sardinian, centum became kentu, preserving the original Latin sound almost perfectly.

From One, Many

So, the next time you hear the vast differences between cento, cent, and ciento, you’ll know it’s not a sign of chaos, but of a beautiful, systematic process of evolution. Palatalization was a phonological earthquake that sent shockwaves through the Latin-speaking world. The resulting fault lines are the very sounds that help define the unique musicality of Italian, the smooth sibilance of French, and the distinctive fricatives of Spanish. They are the living echoes of a great consonant shift that happened centuries ago.