set ablaze vs set on fire

set ablaze and set on fire both are verbs.

Word	Noun	Adjective	Verb	Adverb
set ablaze	No	No	Yes	No
set on fire	No	No	Yes	No

As verbs, set ablaze and set on fire are synonyms defined as:

Other synonyms of set ablaze include set afire, set aflame.

set ablaze (verb)	set on fire (verb)
set fire to; cause to start burning	set fire to; cause to start burning