"Plaintiff Yale is a famous university located in New Haven, Connecticut," said the lawsuit, filed in May in US District Court in Camden, New Jersey. "Yale is a leading university," it adds. "Many distinguished leaders in government, academia, science and business are Yale alumni, including three of the past four United States presidents." And then, lest there be any doubt, "Yale's reputation as a prestigious and elite university resonates not only in the United States, but around the world."

The defendant, Yale Academy, with locations in New Jersey, Pennsylvania and Delaware, can make no such exalted claims - at least not yet. It has been in operation only since 1995. Nonetheless, "It has been known as the best preparation school for college entrance exams", its website says, without specifying quite who has known it that way.

Terry Yang, founder of Yale Academy - or Y2 Academy, as it will be known from August 31 - said he never meant to confuse anyone. In fact, he said, he never meant to invoke the name of that famous, leading, prestigious, elite university. Instead, he just combined his last name - Yang - and that of his wife, Lee.

Sure, his company's logo might have the same blue-and-white colour scheme as that of the university, but so do the logos of countless other companies. And besides, blue is his favourite colour. "No one has ever been confused between Yale Academy and Yale University," he said.

That may not matter, explained James Weinberger, a partner at the law firm Fross Zelnick Lehrman & Zissu and an expert in trademark law. "A university's name is its brand," said Weinberger, who was not involved in the case. "The law says you've got an obligation to go out and police that brand. It's a matter of consistency."

Tom Conroy, a Yale University spokesman, said it generally took action when it considered its name infringed upon. "Our concern is heightened," he continued, by any suggestion of "a programmatic relationship between Yale University and the particular business, as may happen in the field of education."

Similarly Harvard University "actively protects its name and trademarks from unauthorised use around the world, especially in those areas most important to, and most identifiable with, Harvard, such as education research", said Kevin Galvin, a spokesman.

Harvard Maintenance, which offers cleaning services for commercial real estate, is apparently in the clear. But Harvard Academy, in Korea, and the Harvard International School of Management, in India, both got cease-and-desist letters (and have both since changed their names).

Princeton University also "has actively and successfully challenged the use of its name in the past", said Martin Mbugua, speaking on behalf of the university. "Princeton Review is one case in which an arrangement was made through a legal settlement after we challenged the use of the Princeton name."

Place names cannot be trademarked, however. Thus, among many other examples of businesses not connected to the university are the Princeton House condominium, Princeton Laundry and the Princeton Architectural Press. For Columbia University, it is hardly worth bothering. "Columbia is such a common word," said Robert Hornsby, a spokesman.

"It's places and names and Columbia Pictures and Columbia, Missouri, and Columbia College in Chicago."