these are called "Janus words" or self-antonyms. Such as "flammable" and "inflammable". https://en.wikipedia.org/wiki/Auto-antonym https://en.wikipedia.org/wi

these are called "Janus words" or self-antonyms. Such as "flammable" and "inflammable". https://en.wikipedia.org/wiki/Auto-antonym https://en.wikipedia.org/wiki/Auto-antonym