The word “suburb” still raises snickers among some thinkers as a place “out there” where middle-class people without taste reside. The harshest critics dismiss suburbs as the “geography of nowhere.”

Yet the American suburbs have grown so immense and diverse, now housing more than half the U.S. population, that no out-of-date stereotypes can capture their complexity, meaning or future direction.

For example, according to Census data, the number of single people living in the suburbs continues to grow. In fact, some suburbs now have more single households than families with children. Another example: The suburbs in all big metropolitan areas except New York and Chicago contain more office space than the regions’ central business districts.

American suburbs now have essentially the same elements that make a place urban – just arranged in a way that differs enough from traditional central cities.

“Cosmoburbs” is the term used in the forthcoming book “Boomburbs: The Rise of America’s Accidental Cities” to describe wealthy suburbs that are also diverse and that increasingly contain non-traditional households. Leading examples around the nation include Naperville, Ill., Plano, Texas, Bellevue, Wash., and Lakewood and Aurora in Colorado.

In Lakewood, a suburb that is now all but built out, singles and childless couples outnumber households with children. Plans for future growth center on Lakewood’s six stations along the West Corridor line of the FasTracks light-rail system. The areas around the stations will feature high-density, mixed-use developments, including many multifamily units. This type of housing does not typically appeal to families.

Lakewood is following a land-use planning model set by Arlington, Va., in the 1980s when it focused denser growth along the Washington Metro system’s Orange Line. Arlington in 1980, like Lakewood today, contained mostly post-World War II single-family housing in mostly homogenous neighborhoods. But the Orange Line changed the city into a more diverse and vibrant place. Lakewood is poised to do the same over the next decade, as will other suburbs with new light-rail systems, such as Tempe, Ariz.

Aurora is another increasingly diverse suburb. By 2000, less than 60 percent of Aurora was non-Hispanic white. This booming suburb continues to gain minority residents as it grows – it passed 300,000 people in 2005. By 2010, Aurora may even become a “majority minority” city.

Like Lakewood, Aurora will have a branch of the FasTracks system and has started planning for mixed-use development at the stations. Projections are for Aurora to keep growing at its edges as well. Already Colorado’s third-largest city, Aurora may someday rival Denver in overall size.

Even some of Denver’s smaller suburbs have been swept by change. Englewood, just south of the city, was a quintessential 1950s suburb. In fact, Englewood’s Arapahoe Acres neighborhood is the first post-World War II subdivision to be listed in the National Register of Historic Places. Arapahoe Acres’ mid-century modern homes are good examples of the small horizontal ranches that were home to baby-boom families across the U.S. Where in the past such neighborhoods contained mostly households with children, Arapahoe Acres and other similar neighborhoods now have a mix of singles, retirees and childless couples.

Outdated conceptions of suburbia arise from the image developers have marketed to the public. Suburbs are supposed to be safe from the dangers of the cities, for instance. Interestingly, it is this image of safety that attracts a rising influx of minorities. According to the 2000 census, minority groups constituted the largest shift from cities to suburbs in the 1990s. In 65 of the largest 102 metropolitan areas, “minority flight” equaled or outpaced “white flight” to the suburbs.

Much of the Hispanic and Asian gains in the suburbs were due to new arrivals that jumped past central cities. At the turn of the last century, immigrants flocked to the city centers. Today, half of immigrants move directly to suburbs. Asian immigrants, more than any other group, select suburban lifestyles.

In many respects, the Cosmoburb may be the coming America where race is part of the ambiance. Ethnic restaurants and shops with exotic goods draw people into these communities. In such places, it does not matter what race the neighbor is – as long as the lawn is mowed.

The new Cosmoburbs will be part of a global economy. For planners this means that suburbs should not be thought of as merely bedroom communities, but as new economic hubs for an increasingly “brain”-oriented economy. Planners need to think of ways to mix people as well as land uses to build new communities. Suburbs today don’t have less sophisticated economies than cities but are equal to central cities. This shift will require not only new thinking about design, transit and infrastructure in the suburbs, but also new thinking about how the suburbs can truly accommodate singles, seniors, the foreign-born and people of every color.