terminal disclaimer

In the United States, under current patent law, the term of patent is either 20 years from the earliest claimed filing date or 17 years from the issue date, depending on the filing date and the issue date (provided that the maintenance fees are paid in due time):For applications that were pending on and for patents that were still in force on June 8, 1995, the patent term is either 17 years from the issue date or 20 years from the earliest claimed filing date, the longer term applying.For applications filed on or after June 8, 1995, the patent term is 20 years from the earliest claimed filing date.
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also "TD": a statement filed by an owner under 35 USC § 253 (paragraph 2) and 37 CFR § 1.321(b) or (c) to disclaim or dedicate to the public the entire term or any portion of the term of a patent or patent to be granted. A TD may be filed for the purpose of overcoming a judicailly created double patenting rejection.

-- see MPEP 1490 and 37 CFR § 1.321  for more

Context: Patent