Flammable and inflammable

In the old days, inflammable and flammable actually have a subtle difference in meaning.

"Flammable" means something which can be burnt easily, or catch fire easily, like paper, wood and cloth..etc

"inflammable" mean something which easily provides a medium for the act of burning to happen, in other words, serving as fuel. Things like hydrogen, oxygen, gasoline...etc belong to that category.

However, those two meanings seem to blend together nowadays. You will never know that subtle difference if you are not using "chemistry language".

Thanks for the precision, Fly. :D

Priceless means something maybe too good to be put a price on.
Invaluable means something which cannot be measured.

But sincerely, they mean just the same thing, but used differently. I use them the way I described.

So you might say both: ´Thanks for the priceless/invaluable help you gave us´ . They mean the same thing, in a thik sense.

It's like "literally". Some people use the word literally when they actually mean "figuratively" which of course is the opposite.