In the mid-1990s, residents of Nairobi were cautious when traveling through the city's "Rwanda" neighborhoods. Although physically far removed from the genocidal violence in central Africa, this was the area of the Kenyan capital where you were most likely to be mugged or carjacked. A few years later, these areas became known as the "Kosovo" section of the city. By the early 2000s, wandering into one of the "Baghdad" neighborhoods could be iffy.

The frequent shifts in names for areas of town are a product of Sheng, the city's increasingly popular street vernacular that combines both English and Swahili—Kenya's two official languages. A debate has been brewing about it for years: Is Sheng a language or "just" slang? Regardless, tourist translation dictionaries have essentially become useless on the streets of Nairobi because of it.

The vocabulary and meaning of words not only differ in each neighborhood, but some of their definitions change almost daily. Much like with English or any other language, certain slang words change from one generation to the next. But Sheng has completely revamped the vocabulary of an entire city. TV advertisements freely borrow phrases that ignore formal grammatical structure, and radio DJs regularly pepper broadcasts with the latest forms of words. A popular comic book called Shujaaz is written entirely in Sheng. This linguistic phenomenon isn't exclusive to East Africa, of course. Most countries have some version of code-switching, where people select or mix formal and informal languages as the environment or situation calls for—and to fit in with the many different groups they belong to.

Along the streets of Abidjan, Côte d’Ivoire emerged a hybrid language dubbed Nouchi, which is now challenging French as the city's most popular form of speech. Young urbanites from Lusaka, the capital of Zambia, are finding favor with a pidgin language called Town Bemba. Neither of these languages can be translated on Google and are nearly impossible to teach in a traditional setting. Yet slang-influenced languages like these can be heard in nearly every market, bus terminal, and university in Africa.

According to Mokaya Bosire, a University of Oregon professor and expert on Sheng, the origin of these languages can be traced back to the early 20th century, shortly after the arrival of imperial Europeans.

"One of the things that happened with colonialism is urbanization, which wasn't there before," Bosire told CityLab. "And with urbanization you had different people who spoke different languages come together in these towns, which provided [Nairobi] with the perfect condition for Sheng to arise," he explains.

Yet linguistic creativity—or maybe rebellion—in African cities didn't cease when the continent began to receive its independence starting in the 1950s. Modern technology has recently provided young Africans with greater access to hip-hop, African-American culture, and global fashions. Africa's cities are also disproportionately young; as of 2012, the median age of the continent is 20 years old (the median age in North America is nearly 40 years old). This combination of youthfulness and global exposure has left Africa's urban youth with a lot to work with in terms of creating their own terms of communication.

"[Urban Africans] have the knowledge of different languages and they're also exposed to what's going on in the world and how cultures are moving," says Mokaya Bosire. "And the languages that are standard languages—say, English or Swahili—they don't move as fast as these guys want," he adds.

By adopting a fluid, homegrown language, some argue that young Africans are better able to express ideas and experiences specific to their own emerging urban culture. Writing in the Journal of African Studies in 2008, scholar Mungi Mutonya highlighted this claim when analyzing the advent of slang-based advertisements.

Language serves the triple role ... of carrier of culture, as an image forming agent that provides the group with a whole conception of themselves, individually and collectively, and as a transmitter of the images of the world and reality. Thus the circumstances of the language contact environment in African cities present a variety of mixed codes that emerge to satisfy local needs.

The fusion languages springing up now in Africa's cities, however, are likely just the beginning. Africa's urbanization rate will be among the world's fastest from now until 2050. Unless some kind of national language policies are enacted, says Peter Githinji, a linguist specialist at Ohio University, slang-based languages will ultimately become the norm in Africa's burgeoning urban centers.

"[T]he more we're participating in these global cultures and the more we're having rural-to-urban migration," Githinji says, "they're actually going to transform themselves to the point where we're no longer calling them 'urban languages.'"

Top image courtesy of Flickr user Eduardo Gaviña.