President-elect of the United States

President-elect of the United States is the title used for an incoming president of the United States between the general election on Election Day in November and noon Eastern Standard Time on Inauguration Day, January 20. During this time, the elected nominee is not in office yet.
Since the election for U.S. president is not by popular vote, the title is used for the apparent winner. The decision is finalized when votes of the Electoral College, cast in December, are counted by a joint session of Congress in early January. 
If the current president has won re-election, they are not given the title of president-elect because he or she is already in office and not waiting to become president. If a new president is scheduled to enter, then the current-standing one is said to hold the office on a lame duck basis.