ISIS or ISIL: What's the difference? Retired FBI agent says ISIL is more accurate

President Barack Obama calls it ISIL, while others refer to the terrorist group as ISIS or Islamic State. Many have called ISIL the greatest terrorist threat since 9/11. So why is there so much disagreement about what to call this new terrorist group?

Jim Davis is a retired FBI Special Agent in Charge who spent almost two years going after al-Qaida in Iraq and Afghanistan.

"I think that they're all names for the same entity," said Davis. "ISIS is the Islamic State in Iraq and Syria, ISIL is the Islamic State of Iraq and "the Levant," and really that is probably more of an accurate description because "the Levant" covers a larger area."

The definitions of the Levant have included Syria, Lebanon, Turkey, Jordan, Israel, the Palestinian territories and the island of Cyprus.

Davis said ISIL is a more accurate term because it better describes the terrorist group's intent to gain control of the entire region and not limit itself to Iraq and Syria as the name ISIS refers to.

"Islamic State is what they're calling themselves as if they were a nation; we're not recognizing them as a nation," said Davis.

7NEWS also asked Davis how ISIL compares to al-Qaida. He told us the two do share a common ideology, but are two entirely separate terrorist groups.

"The big difference of course, ISIL is grabbing territory, and al-Qaida was just committing terrorist attacks," he further explained.

Davis also said it is important to remember al-Qaida has separated itself from ISIL.

"Al-Qaida has said that these guys are too violent and too extreme even for al-Qaida, that's saying a lot," he said.

We also asked Davis about the size of ISIL to find out how it compares to al-Qaida, with the CIA now saying ISIL has more than 30,000 fighters.

"I think that it's probably very comparable to the strength of AQI [al-Qaida] in the 2000's," he said. "I certainly think that right now ISIL is a greater threat than al-Qaida."