It’s one of the most fundamental and fiercely debated questions in linguistics: what’s the real difference between a language and a dialect? We instinctively feel there’s a line. Spanish is a language; the Spanish spoken in Andalusia is a dialect. But press for a clear definition, and the ground starts to shift. The neat categories we take for granted quickly dissolve into a complex tangle of linguistics, politics, and identity.

There’s a famous quip, often attributed to the Yiddish scholar Max Weinreich, that perfectly captures this dilemma:

“A language is a dialect with an army and a navy”.

This cynical but surprisingly accurate statement gets to the heart of the matter. While linguistic criteria exist, the final decision often has more to do with power, prestige, and politics than with pronouns and pronunciation.

The Linguistic Litmus Test: Mutual Intelligibility

If you ask a linguist for a technical distinction, they’ll likely start with the concept of mutual intelligibility. The rule of thumb goes like this:

• If speakers of variety A can understand speakers of variety B without any prior study (and vice versa), they are speaking dialects of the same language.
• If they cannot understand each other, they are speaking different languages.

This seems simple enough. A New Yorker can understand a Londoner, even with different accents and slang, so American English and British English are dialects of English. However, that same New Yorker won’t understand a Parisian speaking French, so English and French are different languages.

But this criterion breaks down almost immediately. Consider the dialect continuum. Across a geographical area, dialects can change gradually from village to village. A speaker from Cologne, Germany, can understand someone from nearby Aachen. That person from Aachen can understand their Dutch neighbor in Maastricht. But the speaker from Cologne and the speaker from Maastricht might just stare at each other in confusion. Where do you draw the line and say, “Here, German ends and Dutch begins”? The border is a political one, not a linguistic one.

Then there’s asymmetrical intelligibility. Portuguese speakers can often understand Spanish reasonably well, thanks to phonological similarities. However, Spanish speakers find it much harder to understand Portuguese. So, are they dialects or languages? It depends on who you ask.

An Army and a Navy: When Power Draws the Map

This is where the “army and navy” come in. The status of a “language” is often a political and social construct, a declaration of independence and national identity. A standardized, official form of speech is chosen—often the dialect of the capital city or the ruling elite—and designated as the “language”. All other forms are then relegated to the status of “dialects”. Let’s look at some classic examples.

Case Study: The Unraveling of Serbo-Croatian

For decades, people in Serbia, Croatia, Bosnia, and Montenegro spoke what was internationally recognized as a single language: Serbo-Croatian. The varieties were, and still are, almost entirely mutually intelligible. However, following the violent breakup of Yugoslavia in the 1990s, the new independent nations sought to assert their unique identities. Suddenly, what was once one language became four:

• Serbian
• Croatian
• Bosnian
• Montenegrin

Linguistically, the differences are minor, often boiling down to a few vocabulary choices (like the words for “train” or “bread”) and the preferred script (Latin vs. Cyrillic). But politically, they are distinct languages because they are backed by separate states—separate armies and navies. This is perhaps the clearest modern example of politics creating languages where one existed before.

Case Study: The Scandinavian Sisters

Now let’s look at the reverse. Danish, Norwegian, and Swedish are largely mutually intelligible, especially in their written forms. A Swede reading a Norwegian newspaper would have little trouble understanding it. Based on mutual intelligibility alone, they could easily be classified as dialects of a single “Mainland Scandinavian” language. But they are not. Why? Because Denmark, Norway, and Sweden are distinct countries with centuries of separate history, literature, and national pride. They have their own flags, governments, and, yes, armies and navies. Their status as separate languages has never been in question.

Case Study: The “Dialects” of China

China presents the opposite situation. What are often referred to as the “dialects” of Chinese—such as Mandarin, Cantonese, Hokkien, and Hakka—are not mutually intelligible. In fact, they are often more different from each other than Spanish is from Italian. A Mandarin speaker from Beijing and a Cantonese speaker from Hong Kong cannot have a spoken conversation. Linguistically, they are separate languages within the Sinitic language family.

So why call them dialects? Two main reasons: a shared writing system and political unity. For centuries, educated speakers of these different varieties could all read and write the same set of Chinese characters, even if they pronounced them completely differently. More importantly, the Chinese government promotes the idea of a single “Chinese language” (Zhōngwén, 中文) with Mandarin (Pǔtōnghuà, 普通话) as its standard form. This fosters a unified national identity across a vast and diverse country. Classifying these distinct spoken forms as “dialects” is a powerful political tool.

Prestige, Paper, and People

Beyond armies and politics, other factors help elevate a dialect to a language.

Standardization and Prestige: A “language” almost always has a standardized form. This means it has official grammar books, dictionaries, and a body of literature. This standardized version is taught in schools, used in the media, and spoken by those in power. Other varieties are often stigmatized as “incorrect”, “uneducated”, or “quaint”, even if they are linguistically just as valid. Think of how Florentine became standard Italian or how Parisian French became the standard for France.

Self-Identification: What do the speakers themselves think? If a community feels strongly that their way of speaking is a language in its own right and fights for its recognition, that can shift the consensus. The ongoing debate around Scots in Scotland is a perfect example. While some consider it a dialect of English, many of its speakers and proponents advocate for its status as a distinct language, with its own rich literary history.

Conclusion: The Line is a Story, Not a Rule

So, who decides the line between a language and a dialect? The answer is: we all do, but not equally.

Linguists can offer technical guidelines like mutual intelligibility, but these tools are often too blunt to capture the messy reality. The true deciding factors are history, national identity, political power, and social prestige. The distinction is a story we tell about ourselves—about who we are, where we come from, and who holds the power to write the dictionary.

The next time you hear someone correct another’s “dialect”, remember that the line they’re drawing says far more about our societies and our history than it does about language itself.