Refers to the head of state of a republic. Used in formal and news contexts.
アメリカの大統領はホワイトハウスに住んでいる。
The president of the United States lives in the White House.
The presidential election will be held next month.
Familiar, often vocative use, especially toward an actor or someone in a leading role. Can be playful or affectionate, like calling someone 'boss' or 'big guy'.
おい、大統領、今日の舞台も頼むよ。
Hey, boss, I'm counting on you for today's performance too.
うちの大統領がそう言うなら間違いない。
If our big man says so, it must be right.
He took office as the new president last month.
She decided to run in the next presidential election.
The citizens elected a new president by vote.
The president gave a speech to the people.
大統領 refers to a president, the head of state in a presidential system, while 宰相 refers to a prime minister, the head of government under a parliamentary or cabinet system.
executive order; presidential decree
presidential system; presidential government