Crossovers have been one of the most popular segments for more than a decade, but they are also one of the hardest to define.
In the beginning, crossovers were SUV bodies on car frames. They offered better fuel efficiency and a smoother ride while sacrificing some off-road capabilities.
Today, manufacturers label a wide array of vehicles as crossovers. 
The category now includes everything from traditional CUVs to elevated hatchbacks. Some carmakers even label as crossovers what most called station wagons in the past.
Ivan Drury, senior manager of industry analysis at Edmunds, said his firm uses factors such as ride height and trade-in data to categorize a vehicle as a crossover.
Consumers mainly look for all-wheel or four-wheel drive and what they consider good storage capacity.
Crossovers are as popular with used-car buyers as they are on the new side. Black Book reports crossover prices have held steady this year despite a surge of off-lease inventory, indicating strong demand.
Crossover buyers prove very loyal, Drury said. They rank among the top repeat buyers.
Crossover buyers also will pay more for their vehicles, Drury said. Manufacturers often find themselves offering more and more option packages to meet demand even as they increase the prices.
But their loyalty is dispersed, said George Hoffer, professor emeritus at Virginia Commonwealth University.
No one vehicle leads the segment.
Hoffer attributes this to the slow evolution of the crossover.
Unlike other new segments, like muscle cars or minivans, there was no breakthrough leader that everybody else followed.
Hoffer said the first crossover came from American Motors in the ‘70s, when the company tried to maximize its investment in the Hornet platform by putting a Jeep body atop the car frame. The project evolved into the Eagle, which used the Concord platform.
The development continued in bursts and some early versions, such as the Pontiac Aztek and the Chrysler Pacifica, were awkward.
But these types of vehicles broke out in the last decade and grew to one of the largest segments by 2006.
High gas prices helped this growth. Today, some crossovers actually get better gas mileage than sedans.
For the most part, Drury said, they still lag in fuel efficiency.
Will crossovers collapse like the once mighty minivan? Hoffer doubts it.
“I don’t see where these vehicles become dated,” he said. “They’re not unique enough.”
They appeal to a wide range of consumers, as well. Men like the rugged look, women like the sense of safety provided by the high ride and seniors appreciate the ability to easily get in and out of them.
Still, like any market segment, individual versions of crossovers face risks. The biggest now is oversaturation, as each manufacturer, from economy to luxury, comes out with a crossover.
“More choices, more problems,” Drury said.
Again, however, the lack of clear definition helps.
“If it sells, you can call it whatever you want,” Drury said.