1. Seventy percent of the man's body had been burned after the truck caught fire.
2. The house just caught on fire.
(All are from COCA)
I’ve thought that ‘on’ gives the nuance of continuity. So the difference between 1 and 2 would be the property, is the thought. But is there really the difference? Or are there any other differences? Or there are no differences at all?
Best Answer
I think they mean exactly the same thing.
Catch fire is by far the more common idiom; catch on fire seems to be due to influence from on fire.
There also seems to be a regional difference; in the British National Corpus, the ratio of caught on fire to caught fire is 3:144, whereas in COCA, the ratio is 88:542. So whereas caught on fire sounds fairly normal to me (an American), albeit somewhat colloquial, I'm guessing that most British speakers would find it noticeably strange.