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When Vice President Joe Biden and U.S. Rep Paul Ryan face off during their only debate, tens of millions of Americans will tune in to hear them defend their running mates' records.

And that audience Thursday night also will hear lots of budget-related buzzwords, with meanings that may not be entirely clear. Those words are shorthand for policies that could have huge impacts on taxpayers and the annual $1 trillion budget deficit.

Brushing up on terms of the debate can help voters better understand what's really being said on the stage at Centre College in Kentucky.

Even though vice presidents have no constitutional duties other than to break ties in the Senate, they often serve as key presidential advisers. And frequently, they end up serving as president themselves.

Consider the odds: The country has had 44 presidents; nine of them have suddenly taken the presidential oath of office following the death or resignation of a president. Another five former vice presidents have gone on to be elected president. In other words, nearly a third of all presidents have had resumes that included time served as a vice president.

Both Biden and Ryan are considered possible future presidential candidates. Here are some words they likely will use in their debate.

Loophole \ loop hol \

In a budget debate, "loophole" typically refers to gray areas in the tax code. The ambiguity can be used to escape the intent of the law, without technically breaking it. For example, several years ago, Congress offered a tax break that was intended to help small businesses invest in heavy vehicles to upgrade their transportation fleets. The legislation's goal was to strengthen small business. But many small-business owners used the law not to expand fleets but to get a tax credit to buy an SUV for their personal use. During campaigns, politicians often say they will close loopholes to boost government revenues without raising tax rates.

Ryan budget \ rie-ən buj-it \

Besides being the GOP vice presidential candidate, Paul Ryan is chairman of the House Budget Committee. In that role, he has been pushing a plan to reduce the federal deficit by cutting spending. His plan would not balance the budget until 2040, but would reduce annual shortfalls. The most controversial feature involves changing Medicare to offer older Americans a menu of subsidized private insurance plans. Talking about the Ryan budget is usually a way to call attention to the proposed changes in Medicare and reductions in safety-net programs, such as the one offering food stamps.

Energy tax credit \ en-ər-je taks kre-dit \

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