President, presidency, presidential

Capitalize as a title when it immediately precedes a personal name; otherwise lowercase, including appositives.

Avoid abbreviating.

            President Barack Obama but U.S. president Barack Obama

            President-elect Barack Obama; the president-elect

            former president George W. Bush

            then president Bill Clinton

            president of the United States, the president, a president, his presidency

            presidential powers

            president of the Confederacy

           president of France, the president

           Alice Jones, president of CBS; President Jones; the president of CBS

See also: Vice President, Vice Presidency, vice presidential.