And yet, when someone from Bremen is visiting the Swiss Alps, the conversations they hear between locals will likely be incomprehensible to them.

Similarly, outside of China, Mandarin and Cantonese are often referred to as Chinese dialects.

But they're even more dissimilar than Spanish and Italian.

On the other hand, speakers of Danish, Norwegian, and Swedish, which are recognized as three distinct languages, can usually communicate in their native tongues with little difficulty.

And Turkish language soap operas, broadcast without dubbing or subtitles, are some of the most popular shows in Azeri-speaking Azerbaijan.

So, when is a form of speech considered a dialect versus a language?

It seems reasonable that the degree of mutual intelligibility would determine whether two ways of speaking are classified as separate languages or as dialects of the same language.

But as we've seen, there are many occasions where this is not the case.

Perhaps surprisingly, the distinction between a language and a dialect usually has nothing to do with pronunciation, vocabulary, or any other linguistic features.

However, it's not coincidental, either.

It's a matter of politics.

The basis for what's officially deemed a language was shaped by the emergence of European nation states beginning around the 1500s.

In order to establish and maintain centralized governments, clear territorial boundaries, and state-sponsored education systems, many nation-states promoted a standardized language.

Which form of speech was chosen to be the standard language was usually based on what people spoke in the capital.

And while other forms of speech persisted, they were often treated as inferior.

This tradition extended across the globe with European colonization and into modern times.

Italy, for example, has at least 15 of what might be called regional dialects.

One of them, the Florentine dialect, became known as Standard Italian when the country politically unified in 1861.

It was selected because legendary authors like Dante and Machiavelli used it in their original works, and it came to represent an image of Italian national identity that some found particularly desirable.

Later on, in his attempt to establish a unified, fascist state, Italian dictator Benito Mussolini saw language standardization as an important objective.

His government promoted standard Italian while prohibiting other forms of speech from the public sphere, framing them as backward and unsophisticated.

In everything from job applications to court testimonies, standard languages act as gatekeepers around the world.

For instance, one 1999 study showed that landlords responded to apartment inquiries based on what form of speech their prospective tenants used.

When callers spoke African-American Vernacular English, or AAVE, landlords were more likely to reject their inquiries.

When they spoke so-called Standard American English, which is often associated with whiteness, landlords responded more positively.

Both of these forms of speech are considered English dialects.

In the United States, some people have cast AAVE as an incorrect or simplified version of mainstream US English.

But AAVE follows consistent grammatical rules every bit as sophisticated as other forms of English.

Linguists tend to avoid the term "dialect" altogether.

Instead, many opt to call different forms of speech "varieties".

This way, languages are seen as groups of varieties.

So the English language is made up of varieties including Standard British and American English, AAVE, Nigerian English, Malaysian English, and many others.

Each has its own unique history and characteristic pronunciation, vocabulary, and grammatical structures.

But the dividing line between varieties is murky.

Human language, in all its cross-pollinating, ever-evolving glory, naturally resists the impulse to sort it into neat buckets.

Oftentimes, forms of speech exist on a kind of linguistic continuum, where they overlap with others, and the differences between them are gradual, not clear-cut.

And that's the confounding beauty of the dynamic, diverse, and dazzling universe of human communication.