When does the name of a product describe a unique quality that can be trademarked and when does it merely describe attributes that could apply to competing products?  

This is the question raised when the U.S. Patent and Trademark Office recently rejected a trademark application filed by Apple Inc. (Nasdaq:AAPL) over the phrase “iPad Mini.”

The USPTO has said that phrases like “i,” “pad” and “mini” are all descriptive of other types of Internet-connected tablets that are smaller than others in their class.

This might sound like a sematic argument, but the ownership of the phrase “iPad Mini” has real-world implications. For Apple, it means it has yet no trademarked claim to the use of the letter “i” and the two words combined to describe its popular miniature sized version of its iPad, even though it argues that together the name demotes a distinct product owned by the Cupertino, Calif-based technology giant.

Here are the relevant excerpts of the Patent Office letter, which was sent to Apple in late January but only recently made public:

“The letter ‘i’ or ‘I’ used as a prefix and would be understood by the purchasing public to refer to the Internet when used in relation to Internet-related products or services . . . The term ‘pad’ refers to a ‘pad computer’ or ‘internet pad device,’ terms used synonymously to refer to tablet computers, or ‘a complete computer contained in a touch screen’ . . . The word ‘mini’ has been held merely descriptive of goods that are produced and sold in miniature form.”

As for combining the three “merely descriptive” elements to form a trademarked phrase, the agency concluded:

“Both the individual components [the “i,” “pad” and “mini”] and the composite result [“iPad Mini”] are descriptive of applicant’s goods and do not create a unique, incongruous, or non-descriptive meaning in relation to the goods being small handheld mobile devices comprising tablet computers capable of providing internet access. Therefore, the mark is merely descriptive of a feature or characteristic of the goods and registration is refused.

The Patently Apple blog, which first reported the Patent Office letter on Saturday, pointed out that Apple purchased the “iPad” trademark from Fujitsu Ltd. (TYO:6702) on March 17, 2010, just prior to the launch of the tablet. Apple has until late July to respond to the letter with more clarification on its trademark claim.