WASHINGTON -- The change of U.S. administrations has produced a change of terminology in the war against the Islamic State group.

Out goes the name preferred by the Obama administration: the Islamic State of Iraq and the Levant, or ISIL.

In comes the name favoured by President Donald Trump: the Islamic State of Iraq and Syria, or ISIS.

Why?

A Feb. 13 memo from the office of Defence Secretary Jim Mattis says the switch to "ISIS" makes the Pentagon "consistent with" Trump's language in a Jan. 28 directive in which he called for a new plan to defeat the extremist group.

When the Islamic State group swept east from Syria to grab large swaths of Iraqi territory in 2014, the world was divided over how to refer to the extremist group, which traces its roots to al-Qaida in Iraq, which declared an Islamic State of Iraq in 2006. In 2013 the leader of the Islamic State of Iraq, Abu Bakr al-Baghdadi, renamed it the Islamic State of Iraq and al-Sham.

Al-Sham is an archaic word for a vaguely defined territory that includes what is now Syria, Lebanon, Israel, the Palestinian territories and Jordan. It is most often translated as either Syria -- in the sense of a greater Syria that no longer exists -- or as the Levant, the closest English term for the territory it describes and the term preferred by the Obama administration.

Al-Baghdadi later shortened the name to Islamic State, declaring that the territory under his control would be a caliphate, or Islamic state.

In English, the group's name was most commonly translated as the Islamic State of Iraq and Syria (ISIS) or the Islamic State of Iraq and the Levant (ISIL). The Associated Press refers to it as the Islamic State group -- to distinguish it from an internationally recognized state -- or IS for short.

In Iraq and other Arab countries opposed to IS the group is usually called Daesh, an Arabic acronym corresponding to ISIS. The term has a mocking tone and is insulting to IS because it diminishes its claim to have revived the Islamic caliphate. It is also close to the words "dahesh" and "da'es," meaning "one who tramples," making it fodder for puns.