The difference between Shiites and Sunnis is sometimes explained simply as a disagreement over who should have become the leader of the Muslim community after the Prophet Muhammad died nearly 1,400 years ago.

But in Iraq, the divide goes beyond that, partly because of geography and partly because of history. With sectarian tensions rising, Iraqis are paying more attention to the little things that signal whether someone is Shiite or Sunni. None of the indicators are foolproof. But a name, an accent and even the color of a head scarf can provide clues.

Complicating all of this is the reality that many Iraqis have intermarried and that for much of Iraq's history, the two communities have coexisted peacefully. Very rarely has sectarian identity been a life or death matter, the way it is now on some of Baghdad's streets.