Downtown is a term primarily used in North American English to refer to a city's sometimes commercial, cultural and often the historical, political, and geographic heart of the city. It is often synonymous with its central business district (CBD). It may also be a center for shopping and entertainment. Downtowns typically contain a small percentage of a city's employment but are concentrated in services, including high-end services. Sometimes, smaller downtowns include lower population densities and lower incomes than nearby suburbs. It is often distinguished as a hub of public transit and culture.