Inflammable, flammable and combustible are adjectives that can cause confusion, even for native speakers of English. Let’s clear things up!
What do they mean?
Inflammable, flammable and combustible all describe materials or substances that catch fire and burn easily. In this sense, they mean the same thing:
This is a highly inflammable liquid.
We have to lock away flammable liquids such as petrol or paraffin.
The ability of coal to release a combustible gas has long been known.
Note that flammable is the word you will most commonly see on warning labels and safety signs, as it is considered the clearest and most straightforward of the three words and avoids any potentially dangerous confusion!
An extra meaning of combustible
Combustible has one additional meaning that flammable and inflammable do not. It can also be used figuratively to describe a situation that is likely to become difficult or explosive:
We moved to a less combustible discussion about her future.
Be careful!
This brings us to one of the most common mistakes in English. Many people think that inflammable means ‘not flammable’ because the prefix in- often means not in English — think of words like invisible or incorrect. However, this is not the case! Inflammable and flammable mean exactly the same thing. If something is inflammable, it does catch fire easily.
This mixture is highly inflammable. Keep out of the reach of children.
In summary
Inflammable, flammable, and combustible all mean the same thing – easy to set on fire. When in doubt, use flammable, as it is the clearest and most widely understood of the three!
