15 U.S.C. § 1064. Cancellation of registration.

A petition to cancel a registration of a mark, stating the grounds relied upon, may ... be filed as follows ...:

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(3) At any time if the registered mark becomes the generic name for the goods or services, or a portion thereof, for which it is registered,

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If the registered mark becomes the generic name for less than all of the goods or services for which it is registered, a petition to cancel the registration for only those goods or services may be filed. A registered mark shall not be deemed to be the generic name of goods or services solely because such mark is also used as a name of or to identify a unique product or service. The primary significance of the registered mark to the relevant public rather than purchaser motivation shall be the test for determining whether the registered mark has become the generic name of goods or services on or in connection with which it has been used.