Microsoft this week issued a new filing in its legal challenge of Apple's App Store trademark, and is enlisting the help of linguistics to retort Apple's claims. As before, Microsoft's assertion is that the term "App Store" is too generic to trademark. And Apple has itself used the term generically in the past, Microsoft says.

"Apple strains to keep 'App Store' for its exclusive use, even claiming that its online stores are not real stores, only metaphorical ones," the Microsoft filing reads, responding to Apple's previous claims. "But Apple cannot escape the hard truth: When people talk about competitors' stores, they call them 'app stores.' You don’t have to look far to find this generic use ... even Apple's CEO Steve Jobs \\[has used the term generically\\]. And generic use of 'app store' is ... prominent, ongoing and, by Apple's own measure, hundreds of times more frequent than the thin generic use in the cases upon which Apple relies."

Those are fighting words, at least in legalese. But Microsoft has some data too: It says it has found more than 600 incidents of the term "app store" appearing generically in mainstream news publications over a months-long period in 2010. And linguistically, the term "app store" is no more specific than "shoe store" or "grocery store": These things are all generic terms that "describe the thing itself."

"\\[The term\\] App Store is a simple combination of two generic terms that retain their generic meaning when combined, a store offering apps," the Microsoft filing concludes. "The undisputed evidence, including from Apple's own experts and by its CEO Steve Jobs, shows widespread use as the name for a genus of stores and use by competitors. Apple cannot escape the undisputed facts showing that when people discuss the general category of online stores selling apps, they call them 'app stores'."