So, where does this sound come from? Why isn’t bon pronounced “bonn” with a hard ‘n’ at the end? The answer lies in a special category of sounds: nasal vowels.

The Mechanics of a Nasal Vowel

To understand a nasal vowel, we first need to understand a regular, or oral, vowel. When you say vowels like “ah”, “ee”, or “oh”, all the air from your lungs travels up and exits exclusively through your mouth. In the back of your mouth, a little flap of tissue called the velum (or soft palate) is raised, acting like a valve that blocks off the passage to your nasal cavity.

Now, think about nasal consonants like ‘n’ or ‘m’. To make these sounds, you do the opposite. You block the airflow in your mouth (with your tongue for ‘n’, your lips for ‘m’) and lower your velum. This re-routes the entire airstream through your nose. You can feel this by saying a long “mmmm” sound and pinching your nose—the sound stops instantly.

A nasal vowel is the magical hybrid of these two processes. To produce one, you shape your mouth for a vowel (like “ah”) but you also lower the velum. This allows air to flow out of both your mouth and your nose simultaneously. The result is a vowel with a distinctive resonant, “nasal” quality. It’s not a vowel followed by a consonant; the nasality is part of the vowel itself.

The Great Nasal Merger: A Historical Shortcut

French and Portuguese didn’t always have these sounds. They inherited their vocabulary from Vulgar Latin, the language of the Roman Empire, which had no nasal vowels. In Latin, a word like BONUM (good) was pronounced with a distinct vowel ‘o’ followed by a distinct consonant ‘n’ sound. So, how did we get from BONUM to the French bon [bɔ̃]?

The process, which happened over centuries, is called nasalization and deletion. Here’s a step-by-step breakdown:

1. The Original State: In Old French, a combination like ‘on’, ‘an’, ‘en’, or ‘in’ was pronounced as two separate sounds: an oral vowel followed by a full ‘n’ or ‘m’ consonant. For example, vent (wind), from Latin VENTUM, would have sounded something like “vent” as an English speaker would say it.
2. Anticipatory Nasalization: Speakers, in their natural tendency toward efficiency, began to get a little “lazy”. When pronouncing a vowel before a nasal consonant, they started anticipating the ‘n’ or ‘m’ sound. This meant they began lowering their velum slightly during the vowel, “leaking” some air through the nose. The vowel itself started to become nasal. Our “vent” now sounded more like “v-eñ-t”, with a nasal quality bleeding into the vowel.
3. The Merger: Over time, this nasalization of the vowel became so prominent that the original consonant sound was no longer necessary. It was redundant. The ‘n’ or ‘m’ sound was completely absorbed into the vowel, leaving behind only its nasal quality as a “ghost”. The consonant sound at the end of the syllable was deleted entirely.

This is why in modern French, the ‘n’ or ‘m’ in combinations like an, en, in, on, un are typically not consonants at all. They are merely spelling conventions—orthographic markers—that tell the reader to produce a nasal vowel.

Examples of the French Nasal Shift:

• Latin CANTĀRE → French chanter (to sing), pronounced [ʃɑ̃te]. The “an” is a single nasal vowel.
• Latin VĪNUM → French vin (wine), pronounced [vɛ̃]. The “in” is a single nasal vowel.
• Latin BONUM → French bon (good), pronounced [bɔ̃]. The “on” is a single nasal vowel.

Portuguese: A Parallel Journey with a Tilde

Portuguese underwent a very similar, though independent, historical process. Vowel + ‘n’ or ‘m’ combinations also merged into resonant nasal vowels. This is most obvious in words ending in -ão, -ãe, and -õe, which create some of the most characteristic sounds in the language.

• Latin PĀNEM → Portuguese pão (bread), pronounced [pɐ̃w̃].
• Latin CANEM → Portuguese cão (dog), pronounced [kɐ̃w̃].
• Latin MANUM → Portuguese mão (hand), pronounced [mɐ̃w̃].

What makes Portuguese particularly interesting is its orthography. While French uses the now-silent ‘n’ and ‘m’ to signal nasality, Portuguese often uses a dedicated symbol: the tilde (~). This diacritic, called a til in Portuguese, is a clear and unambiguous marker placed directly over the vowel to show that it’s nasal. The word pão isn’t “pa-o”; the tilde tells you the ‘a’ sound itself must be nasalized.

Of course, just like in French, Portuguese also uses ‘n’ and ‘m’ as nasal markers, especially in the middle of words (e.g., cantar, sempre).

The Road Not Taken: Spanish and Italian

The best way to appreciate this unique development in French and Portuguese is to look at what happened in their sibling languages. Spanish and Italian, which also evolved from Vulgar Latin, simply didn’t take this path. They kept the vowel and the nasal consonant as two distinct sounds.

Let’s compare the same Latin words:

*Note: Portuguese “vinho” developed differently, but the principle of nasality in words like “cantar” remains.

Listen to a Spanish or Italian speaker say bueno or buono. You clearly hear the “n” sound. The vowel preceding it is a pure, oral vowel. The velum stays up during the “ue” and “uo”, and only lowers for the final ‘n’ consonant. There was no merger.

A Sound That Defines a Language

This phonological shift is more than just a linguistic curiosity. It’s at the very heart of the sound and rhythm of French and Portuguese. For language learners, understanding that the ‘n’ or ‘m’ is often just a marker is a crucial breakthrough. You must resist the English-speaker’s urge to pronounce it as a hard consonant. The word maison isn’t “may-zonn”; it’s a smooth, open sound that flows through the mouth and nose together.

The next time you hear that nasal twinge, you’ll know exactly what it is: not a consonant, but a special kind of vowel—a beautiful, resonant ghost of a consonant that vanished long ago, leaving its melodic echo behind.