English Practice

The words “flammable” and “inflammable” both mean “able to catch fire easily.” This seems confusing because the prefix “in-” often means “not” (like incomplete or invisible), but in this case it has a different origin and meaning.

1. Origin of the words
Both words come from the Latin verb “flammare,” which means “to set on fire.” The word “inflammare” in Latin meant “to ignite or set ablaze.” From this root we get inflammable, meaning something that can easily catch fire.

2. Why “inflammable” doesn’t mean “not flammable”
In inflammable, the prefix “in-” does not mean “not.” Instead, it means “into” or “toward,” indicating the action of being set into flames. So inflammable literally means “capable of being set into flames.”

3. Why “flammable” was introduced
Because many people thought “inflammable” meant “not flammable,” safety organizations started using “flammable” instead to avoid confusion. For example, warning labels on fuel tanks, chemicals, and gases usually say “flammable.”

4. Modern usage
Today:

Flammable = easily catches fire (preferred on safety labels)

Inflammable = also means easily catches fire, but used less in safety contexts because it can confuse people.

Example:

Petrol is flammable.

Petrol is inflammable.
Both sentences mean the same thing.