Opportunity Cost

Opportunity cost, as defined by my two economics teachers, is what one has to give up when making decision - a trade off, in essence. An example is that if I buy a new video game , I will not be able to buy my mother a birthday gift...I bought the game. Another, not so economic example is that if I dedicate my time to running, I will be unable to join the fencing club. The U.S government has to make trade offs all the time. Should they further the "War on Terror" by buying more, bigger weapons. Or should they invest in building roads.