Do the words flammable and inflammable mean same thing?

Yes, "flammable" and "inflammable" mean the same thing. They both describe something that is easily set on fire.

However, "flammable" is the preferred term today because "inflammable" can sometimes be misinterpreted as meaning "not flammable." This is because the prefix "in-" can sometimes mean "not," as in "incapable" or "inactive."

To avoid confusion, it's best to stick with "flammable" when referring to something that is easily set on fire.