Difference between ‘to be on fire’ and ‘to burn’

by Jakub Marian

Tip: See my list of the Most Common Mistakes in English. It will teach you how to avoid mis­takes with com­mas, pre­pos­i­tions, ir­reg­u­lar verbs, and much more.

There is no significant difference between “something being on fire” and “something burning”, where “something” is a flammable material. However, the two expressions are not interchangeable in many other situations. For example, one can say that “a fire is burning”, but not that “a fire is on fire”:

More 50 large fires were burning in the region this morning.

Another difference is that “burn” can be used transitively (i.e. “someone can burn something”), but “being on fire” cannot:

The spy has burnt all the important documents.
(Note that “burned” is the preferred form in the US and “burnt” in the UK.)

The transitive form of “to be on fire” is “to set on fire”, which is synonymous with “to ignite, to cause to begin to burn”, but that is not the same as “to burn”. When something was burnt (or burned), the implied meaning is that it was destroyed, whereas when it was merely set on fire, it was in flames, but it may still be undamaged. You could say, for example,

The spy has set all the important documents on fire, but we were able to put them out before they were significantly damaged.

Other differences between “burning” and “being on fire” are related to their idiomatic meanings. “On fire” can be used in the sense of “achieving great results”, used especially in sports commentary, e.g.

Wow, what a save! The goalkeeper is on fire tonight!

“Burning”, on the other hand, can be used in the sense of “urgent and important”, usually when referring to a question or an issue, e.g.

The Security Council is facing a number of burning issues.

or in the sense of “strong, extreme” when talking about feelings, e.g.

He was consumed by a burning desire to win.

By the way, if you haven’t read my guide on how to avoid the most common mistakes in English, make sure to check it out; it deals with similar topics.