This week's Washington Post article on the rise of the fast-casual restaurant in America accomplishes something that most reports on the trend do not. That is, it attempts to define the term beyond the usual "Oh, you know, like Chipotle."

Though there is plenty of hard data to illustrate just how popular this indefinable concept has become  a $21-billion-per-year business in the U.S. alone, according to one such estimate — the category remains "only loosely defined at best," as WaPo notes. Even the industry groups that make it their business to know these things tend to disagree about whether a particular (non-Chipotle) chain qualifies. Buffalo Wild Wings, with its mix of both quick and full-service options, is a prime example.

Defining fast casual begins with what it is not: traditional fast food. It is perceived to be healthier. Or at least fresher. And by extension, we know something else it is not: cheap. We're talking $9 to $13 per ticket on average, compared to about $5 in an old-school fast-food joint. Beyond that, the definition gets a little fuzzy without name-dropping the standard-bearer.

About the closest thing to an honest-to-goodness definition is a set of ten different "markers" that, according to industry research firm Technomic, help to distinguish the Chipotle-esque from the old guard. Per WaPo:

The quality of the food, the use of better ingredients, food that is wholesome, a perception of freshness, first-rate decor, fair pricing, fast service, friendly employees, flexible offerings, and a full view of how the food is prepared.

Still confused? Just wait. As more conventional fast-food operators, like struggling McDonald's, begin to adopt the practices of contemporary fast-casual chains, the lines could become even blurrier. Says Technomic's Darren Tristano: "If you think it's hard to tell what makes a restaurant fast casual today, it's only going to get more confusing."

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