The term of a patent is the maximum period during which it can be maintained into force. It is usually expressed in number of years either starting from the filing date of the patent application or from the date of grant of the patent. In most patent laws, renewal annuities or maintenance fees have to be regularly paid in order to keep the patent in force. Otherwise the patent lapses before its term. The term of a patent or specific "claims" in a patent may also be curtailed by judgment of a court, as where a claim or patent is held "invalid" under the relevant law, and thus no longer enfo...