The case may be even more tangled with Hezbollah, which is credited across Lebanese factions with forcing Israel to abandon its 20-year occupation of southern Lebanon, defeating Israel in a 2006 war and placing its members in Lebanon’s government and Parliament.

“If Obama thinks these organizations are terrorists, there will never be peace,” said Hany Hassan, 29, who was selling flowers from his uncle’s shop in the quiet Cairo suburb of Maadi. “Bin Laden, he is a terrorist. These organizations, if America thinks they are terrorists, they will have to convince us.”

There are certain cases where there is a greater consensus over what is terrorism, such as the Sept. 11 attacks by Al Qaeda, the attack on a school in Beslan, Russia, bombings in Bali, Spain and London (though even here, it is not unanimous). But in this region, for example, the invasion of Iraq is often referred to as a terrorist act.

The issue of who is a terrorist often stirs strong emotions and fuels diplomatic conflicts. Iranian officials, for example, recently excoriated ambassadors from the European Union for having removed the People’s Mujahedeen Organization of Iran from the list of banned terrorist organizations. Iran considers it a terrorist group committed to overthrowing the state.

“The Islamic Republic of Iran strongly condemns the double standards of the European Union regarding the phenomenon of terrorism,” Deputy Foreign Minister Mehdi Safari told the ambassadors in Tehran.

Ron Pundak, director of the Peres Center for Peace in Israel, said, “I accept that Hamas and Hezbollah are terrorist organizations, but I think we should speak with them to pursue our objectives.” He acknowledged his view was out of sync with Israeli public opinion.

What has happened, he and other regional analysts said, is that the use of the term “terrorist” has become a simplistic point, counterpoint offensive of its own, reflecting the growing influence of radicalism on both sides. It is often used to cloud issues, to avoid having to talk and to try to appear to take the moral high ground, they said.