Русско-англо-русский юридический словарь

The term of a patent is the maximum period during which it can be maintained in force. It is usually expressed in a number of years either starting from the filing date of the patent application or from the date of grant of the patent. (Wikipedia)

A Force Majeure clause (French for "superior force") is a contract provision that allows a party to suspend or terminate the performance of its obligations when certain circumstances beyond their control arise, making performance inadvisable, commercially impracticable, illegal, or impossible. (ContractStandards)

The importance of the force majeure clause in a contract, particularly one of any length in time, cannot be overstated as it relieves a party from an obligation under the contract (or suspends that obligation). (Wikipedia)

Supplemental agreements are legally binding documents that are used to modify contracts that are already in force. This type of document is sometimes used as a means of allowing the existing agreement to remain in place with the same ending date, while adding or removing some provisions or terms to the working relationship. A supplemental agreement is often an ideal solution when there is no desire to renegotiate an entirely new contract to take the place of the current agreement. (WiseGEEK)