Apple has responded to Microsoft’s allegations that “App Store” cannot be trademarked by noting other generic terms that have been trademarked because of their unique nature. It even had a linguistics expert declare “App Store” was a noun for Apple’s service, according to the legal documents filed to the Trademark Trial and Appeal Board by both companies.

“Having itself faced a decades-long generic challenge to its claimed Windows mark, Microsoft should be well aware that the focus in evaluating the mark is on the mark as a whole and requires a fact-intensive assessment of the primary significance of the term to a substantial majority of the relevant public,” said Apple’s attorneys in a 63-page filing on Feb. 28. Apple also believes it is fair to say that consumers associate both the blue App Store graphic pre-installed on all iPhones and iPads and the “app” term exclusively with Apple, based on its history of use.

In Microsoft’s 27-page filing on Jan. 10, the company’s attorneys maintained that “App” is a common generic name for the goods offered in Apple’s store and is in “widespread use by Apple and others.” The term “store,” Microsoft said in its filing, is just too generic to be trademarked at all.

Microsoft’s filing also mentioned that many people—including Apple’s CEO Steve Jobs—have used the term “app store” to mean any store selling mobile applications. The filings cited an interview Jobs had in January where he commented on Amazon’s, Google’s, Verizon’s and Vodafone’s Amazon’s app stores.

Apple, in its reply, cited linguistics expert Robert Leonard who, based on “empirical evidence,” determined that the term “App Store” is, in fact, a proper noun for Apple’s online store.

The U.S. Trademark Trial and Appeal Board has yet to deliver a decision in the case.