Sheng: the expanding domains of an urban youth vernacular

African multilingualism is changing the languages and identities of urban communities, and indeed entire nations. Sheng, a non-standard variety of Kenyan Swahili closely associated with Nairobi's urban youth, continues to grow in numbers of users, and to expand its domains of use. Like other 'youth languages' of Africa as elsewhere, it is deployed as a marker of social identity, and is characterised by extensive code-mixing within a Swahili matrix, thus placing it on a continuum of Kenyan ways of speaking, or 'Kenyanese'. The code is also an outcome of language dynamics within a socially stratified, multilingual society in search of a modern identity. In this article, I discuss Sheng's recent entry into mainstream domains of language use in Kenya such as the media, politics, education and corporate advertising. Shifts in population dynamics, as well as changed infrastructure and communications, have also aided its spread into peri-urban Nairobi and rural Kenya. This marks a step across an important threshold in Sheng's capacity to alter Kenya's language ecology in significant ways, as it morphs from a youth language into an urban vernacular.