A filibuster is a tactic used in the U.S. Senate to delay or block a vote on a measure by preventing debate on it from ending. The Senate's rules place few restrictions on debate; in general, if no other senator is speaking, a senator who seeks recognition is entitled to speak for as long as they wish. Only when debate concludes can the measure be put to a vote. Rule XXII of the Standing Rules of the Senate allows the Senate to vote to limit debate by invoking cloture on the pending question. In most cases, however, this requires a majority of three-fifths of senators duly chosen and sworn, so a minority of senators can block a measure, even if it has the support of a simple majority.