Can someone explain why "inflammable" means flammable, although it clearly contains a negation...,(reply>), Unpossible,(reply>), @Logo So is the negation "uninflammable"? My computer marks it as wrong. Unflammable? Marks that too.,(reply>), from inflame-able.<br><br>to flame means to burn something with flame, and to inflame means to be ignited. Since -able has both the meaning of "ability to do something" and "ability to be done something to", Both flammable and inflammable means "to be able to catch on fire"<br><br>the in- prefix actually don't only have the meaning of negation. Inward, inside, income etc uses "in" to represent the preposition "in".,(reply>), in flame - able.,(reply>), intact, inept, inter, inflame, infuse, infiltrate, indoctrinate, indicate, inform, infect, infraction, indite, ingenuous, ingenious, inhabit, inject, injure, intense, intend, intent, increase, incur, inculcate, inert, insert, involve, invoke, invective, inoculate, incense, incentive, inquire, industry, indicate, indubitable, inflection