There are two types of vetoes available to the president. The regular veto, called a “qualified negative veto,” is limited by the ability of Congress to gather the necessary two-thirds vote of each house for constitutional override. The other type of veto is not explicitly outlined in the U.S. Constitution, but is traditionally called a “pocket veto.” As an “absolute veto” that cannot be overridden, it becomes effective when the president fails to sign a bill after Congress has adjourned and is unable to override the veto. The president’s veto authority is a significant tool in legislative dealings with Congress. It is not only effective in directly preventing the passage of legislation undesirable to the president, but serves as a threat, thereby bringing about changes in the content of legislation long before the bill is ever presented to the president.