More than six:
Andrew Johnson, Taft, Franklin Pierce, George HW Bush, John Adams, John Quincy Adams, Jimmy Carter, Gerald Ford, James Buchanan, JFK, James Garfield, Zachary Taylor, Hoover, Harding, and probably others I'm forgetting. Some of these Presidents died in office, others failed to be reelected.
Adams Adams Vanburen Harrison Tyler Polk Taylor Fillmore Pierce Buchanan Johnson Hayes Garfield Arthur Harrison McKinley Taft Harding Coolidge Hoover Kennedy Ford Carter Bush
As a group one-term presidents are not so successful which is why they were one-term presidents. Polk refused to run for a second term and he was probably the most successful one-termer. Taft would very probably have won a second term if Theodore Roosevelt had supported him instead of breaking with with his party and running as an independent against him.
No, that is not a requirement.
6
John Adams is one of them.
An Israeli Presidents' term is 7 years long, and they may only serve one term. Before 1993, a term was 5 years long, and presidents were limited to two terms.
The length of a term for the President of the United States is four years. A president may one serve two terms in his lifetime.
4 years
During Thomas Jefferson's first term, the Vice President was Aaron Burr. Jefferson's second term as President was George Clinton's first term as Vice President (Clinton was one of the two U.S. Vice Presidents who served under two Presidents).
find a counterexample to the statement all us presidents have served only one term to show statement is false
Brazilian presidents are elected for a term of 4 years. They can be re-elected for one additional term.
All presidents are typically eligible to serve more than one term.
George Washington is the president that appointed the most Supreme Court Justices. There have been only seven US Presidents that served only one term.