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Machines Machines are eligible subject matter that may be patented. Machines are any apparatuses that have moving parts, such as, for example, an internal combustion engine.

Maintenance Fees Maintenance fees are required to keep the patent in force. Failure to pay maintenance fees in time results in the expiration of the patent.

Maintenance fee reminder The Unites States Patent & Trademark Office may send reminders as to when a maintenance fee is due.

Manual of Patent Examination Procedure (MPEP)
The Manual of Patent Examination Procedure sets forth the procedures carried out by the patent office, particularly the examination of patents.

Microorganisms as patentable subject matter Microorganisms produced by man are eligible subject matter that may be patented in the United States since Diamond v. Chakrabarty in 1980.

Multiple dependent claims Multiple dependant claims are claims that refer to more than one dependant claim. While some countries' patent practitioners use these types of claims, they are frowned on in the U.S. as poor practice.