Imagine telling a Scot that they speak a dialect of American English, or telling a Brazilian they’re just speaking “European Portuguese with an accent.” You’d likely get an earful. Yet, a few decades ago, millions of people from the snowy Alps of Slovenia to the sun-drenched coast of Montenegro would have said they spoke a single language: Serbo-Croatian.

Today, that unified language is officially gone. In its place are four distinct, constitutionally recognized languages: Serbian, Croatian, Bosnian, and Montenegrin. While speakers can still understand each other almost perfectly, the linguistic gap between them is widening every year. This isn’t a natural, slow-drifting evolution. It’s a conscious, politically charged process of linguistic divergence. So, how and why are these sibling languages deliberately growing apart?

A Shared Past: The Story of Serbo-Croatian

To understand the breakup, we first have to understand the union. The idea of a single language for the South Slavs (Jugoslavs) was born in the 19th century. Intellectuals, dreaming of a unified state, sought to create a unified literary language. The landmark 1850 Vienna Literary Agreement, spearheaded by Serbian reformer Vuk Karadžić and Croatian linguist Ljudevit Gaj, laid the groundwork.

They standardized the language based on the widespread and mutually intelligible Shtokavian dialect. For over a century, and especially during the time of Yugoslavia (1918-1992), “Serbo-Croatian” (or “Croato-Serbian”) was the official language. It was a classic example of a pluricentric language—a single language with several official standard versions, much like English (UK, US, Australian) or Spanish (Spain, Latin American varieties).

Even then, differences existed:

• Script: Serbs predominantly used the Cyrillic alphabet, while Croats used the Latin alphabet.
• Vocabulary: The “Western” variant (in Croatia) and the “Eastern” variant (in Serbia) had lexical preferences. For example, “train” was vlak in the West and voz in the East.

These differences were seen as regional variations within one linguistic system. That all changed in the 1990s.

The Breakup of a Nation, The Breakup of a Language

The violent dissolution of Yugoslavia was a catalyst for linguistic separation. As new independent nations—Croatia, Bosnia and Herzegovina, and later Montenegro—emerged, language became a cornerstone of their new national identities. If you are a distinct nation, the thinking goes, you must have a distinct language.

The famous linguistic maxim, “A language is a dialect with an army and a navy”, has never been more relevant. Each new state began actively standardizing its own version of the language, emphasizing differences and minimizing similarities. This process is known as linguistic purism.

The Mechanics of Divergence: How They Are Growing Apart

The separation isn’t happening through massive grammatical overhauls. Instead, it’s a meticulous, word-by-word process, focusing on vocabulary, with some minor grammatical points thrown in for good measure.

Vocabulary: The Biggest Battlefield

This is where the most visible changes are occurring. Each group is making conscious choices about which words to use, promote, and even invent.

Croatian: The Purist Approach
Croatia has engaged in the most aggressive form of linguistic purism. The goal is to “cleanse” the language of words seen as foreign, particularly “Serbianisms” and international loanwords. This involves:

• Reviving archaic words: Bringing back old Croatian words that had fallen out of use.
• Coining new words (neologisms): Creating new words from Slavic roots.

Some classic examples include:

• Airplane: zrakoplov (lit. “air-sailer”) in Croatian vs. the international avion in Serbian and Bosnian.
• Thousand: tisuća (an older Slavic word) in Croatian vs. the Greek-derived hiljada in Serbian and Bosnian.
• Football (Soccer): nogomet (lit. “leg-toss”) in Croatian vs. the English-derived fudbal in Serbian and Bosnian.
• History: povijest in Croatian vs. the international istorija in Serbian and Bosnian.

Bosnian: The Middle Ground with an Eastern Flavor
Bosnian occupies a position between Serbian and Croatian but seeks to establish its uniqueness by embracing its Ottoman heritage. This means a greater acceptance and promotion of Turkisms—words of Turkish, Arabic, or Persian origin that entered the language during centuries of Ottoman rule.

While many of these words exist across the region, they are often given more prominence in formal Bosnian. For example:

• Coffee: While kafa is common, the form kahva is often promoted as distinctly Bosnian.
• Words like merhamet (compassion, charity) and avlija (courtyard) are emphasized as part of the Bosnian linguistic identity.

Serbian: The Keeper of the Status Quo?
Serbian is generally more receptive to international loanwords (like avion and fudbal). It is often positioned as the direct continuation of the mainstream Serbo-Croatian standard. While it also has its own purist movements, they tend to be less influential in everyday language than in Croatia. The most significant marker of Serbian identity remains the prominent use of the Cyrillic script, which is officially promoted by the state, although the Latin script is also widely used and understood.

Montenegrin: The Newest Standard
The standardization of Montenegrin is the most recent and politically charged development. To carve out a unique linguistic space, Montenegrin linguists codified two new letters for their alphabet (based on both Latin and Cyrillic) to represent sounds they argue are distinct to Montenegrin dialects: Ś and Ź.

• For example, “tomorrow” is sutra in Serbian, Croatian, and Bosnian, but the prescribed Montenegrin form is śutra.

This top-down move is highly controversial and not universally adopted even within Montenegro, but it is a powerful statement of linguistic independence.

Minor Grammatical Differences

Prescriptivists also highlight and enforce minor grammatical distinctions. The most famous example is the use of the infinitive vs. the `da` + present tense construction for “want to do something.”

• Croatian standard prefers: Želim čitati. (I want to read.)
• Serbian standard prefers: Želim da čitam. (Lit. “I want that I read.”)

In reality, both forms are used and understood by all speakers, but schools and official media in each country now push “their” version as the correct one.

Are They Really Different Languages?

This is the million-dollar question. From a purely linguistic perspective, based on mutual intelligibility, they are not separate languages. A Serb, a Croat, a Bosniak, and a Montenegrin can sit at a table and have a fluent, effortless conversation. The differences are smaller than those between Castilian Spanish and Mexican Spanish, or even between Glaswegian and Cockney English.

However, from a sociolinguistic and political perspective, they are four different languages. Because their speakers and governments identify them as such, they function as separate languages in education, media, and law. Language is not just a tool for communication; it’s a powerful symbol of identity, culture, and sovereignty.

The divergence of Serbian, Croatian, Bosnian, and Montenegrin is a fascinating, real-time experiment in language creation. It shows us that the line between “language” and “dialect” is often drawn not by linguists, but by politics, history, and the human need for a unique identity.