This lesson provides an overview of the central role of "use" in United States trademark law. It examines how the policy justifications driving trademark law (1) justify generally requiring use to obtain and maintain trademark rights and related infringement considerations and (2) define sufficient use for those trademark law purposes. It also addresses and explains the few specific exceptions to the use requirement. The lesson assumes a basic knowledge of trademark policy, the distinctiveness classification system and infringement. The lesson can be used as an overview summary at the end of a course or foundationally before a more detailed discussion of (1) acquisition of trademark rights and the related limitations, (2) loss of those rights, or (3) the role of use in federal registration.