A more thorough explanation:

A patent-term guarantee is a legal right given to inventors to extend the term of their patent if the U.S. Patent and Trademark Office (PTO) caused a delay in the application process. This means that if the PTO took too long to review the application, the inventor can get extra time added to the patent's term.

The extension can be up to five years and is granted if the delay was caused by an interference proceeding or appellate review, if the PTO missed a statutory deadline for certain steps in the prosecution, or if the PTO failed to grant the patent within three years of the filing date. This guarantee was put into effect on May 29, 2000.

Let's say an inventor filed a patent application in 2010, but the PTO did not grant the patent until 2015. In this case, the inventor could use the patent-term guarantee to extend the term of the patent by up to five years, since the PTO took longer than three years to grant the patent.

Another example would be if the PTO missed a deadline for a certain step in the prosecution process, causing a delay in the application. In this case, the inventor could also use the patent-term guarantee to extend the term of the patent.

These examples illustrate how the patent-term guarantee works and how it can benefit inventors who have experienced delays in the patent application process.