A utility patent contains written claims which distinguish a given article, method, apparatus or composition of matter from prior inventions. The invention must be useful, new, and not obvious from prior inventions.

A "provisional" utility patent application never is published, examined or granted. It dies on its first birthday. A provisional application is useful for securing a filing date for an invention, providing it enables other people of ordinary skill in the field to make and use the invention.

A design patent contains drawings or photos which distinguish the appearance of a given article from that of other articles. The drawings are the patent claim, and therefore they must be accurate, clear and consistent.

Plant patents may be granted for certain categories of plants. Non-patent protection is available for other types of plants under the Plant Protection Act.

The owner of a patent may apply for reissue of his patent if he mistakenly claimed more or less than he had a right to. Narrower claims can be applied for by reissue any time; broader claims must be applied for within two years of the date of patent grant. Subject matter given up in order to obtain the patent originally cannot be recaptured.

Either the patent owner or anyone else may request that the Patent Office re-examine a granted patent, on the ground that there is a substantial new question of patentability. This question most often results from newly discovered prior art that the examiner did not consider; however, new interpretations of prior art may be sufficient. Reexamination proceedings may be either ex parte, in which case only the patent owner can participate in the process after it is declared, or inter partes in which case the reexamination requestor has an opportunity to participate in the process.