A patent, while commonly misunderstood as a right to do something, is actually a right to exclude others from doing something. On our land or in our home, we may be restricted (making excessive noise) or prohibited (growing illegal drugs) from doing certain things. With few exceptions, however, we have the right to exclude others from our home or land. In the world of patents, the right is a grant from the government to exclude others from the making, using, or selling our invention. Included in that right is the right to license the invention to others to make, use, or sell it. And, like the title to our land or home, the patent claims define the limits of our patent and our patent may be sold or given to others (by an assignment). Currently, utility patents expire twenty years from the data of filing, but maintenance fees must be periodically paid to the U.S. Patent and Trademark Office to keep the patent in force. Design patents expire 14 years from the date of issue, and no maintenance fees are required to keep the patent in force.