WASHINGTON — When President Barack Obama raises his hand to take the oath of office Monday in a majestic inauguration ceremony, he’ll already be 24 hours into his second term.

He’s first taking the oath in private on Sunday, Jan. 20, the date that the Constitution says one presidential term ends and another begins. The second oath is show business, with theatrical props that include a stack of two Bibles: one used by Abraham Lincoln and one used by Martin Luther King Jr.

Remarkably, for a man elected to only two terms, Obama’s staged recitation Monday will mark the fourth time he’s sworn the presidential oath. It turns out that some oaths mean more than others, even when the words sound the same.