They are both different. President means the president of a country that is the leader of the country Presidency means the period of someone is a president. like his presidency lasted 8 years.
If I ____ for the presidency three year ago, it would be me who's sitting in...quot; then it would be: If I ran for the presidency, it would be me who's sitting in presidential place...
chief of Ceremonial of this Presidency of the Republic 意思是:共和國的這個總統職位禮儀的首領