In the United States, the president is responsible for either signing or vetoing bills passed by Congress. Veto power is rarely exercised, as Congress knows that it can only override a veto with a two-thirds vote of both Senate and House.
Veto, which is derived from the Latin phrase "I forbid," may only prevent action, never implement it. Vetoes have a long history, beginning in ancient Rome where consuls could veto one another's actions and a tribune could veto an act of the Roman senate. Many countries and all U.S. states have a version of the veto as well.
The line-item veto allows a head of state to veto specific appropriations within a larger bill. In 1996, President Clinton signed a line-item veto bill into law, giving the next president the right to make such vetoes. Several members of Congress immediately challenged it, and it was overturned by the Supreme Court in 1998 as unconstitutional. Nevertheless, other versions of this bill continue to be debated at a national level. A number of U.S. states allow the line-item veto as well as the amendatory veto, which allows the governor to make line changes, and the reduction veto, which allows the governor to reduce appropriations amounts without vetoing an entire appropriation or bill.