Definition of Interim Title
What does the term "interim title" mean in the world of mixed martial arts? What is meant by an "interim title" in the UFC?
Over the past number of years, the number of interim title fights in the UFC has spiked dramatically, mainly due to the company's insistence of having a title fight headline their numbered PPV cards.

In fact, UFC 236 will feature two interim title fights - Max Holloway vs Dustin Poirier and Israel Adesanya vs Kelvin Gastelum.
Five years ago, interim title fights were fairly rare and now they seem to take place all the time.
Here are some of the circumstances that can lead to interim title fights:
1) Champion is suffering from some sort of longer-term injury or ailment (Robert Whittaker, Middleweight)
2) Champion is suspended for a significant period of time (Khabib Nurmagomedov)
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Interim title fights are not especially popular with fans, though the UFC implements them because they want to "keep things moving" when a champion is sidelined.