The word "in-operative" describes something that does not have any effect or is not functioning. Its antonyms, on the other hand, include words that describe something that is working effectively or having an impact. Some antonyms for "in-operative" include active, effective, operative, functional, useful, efficient, productive, and potent. For instance, an active or operative machine can effectively perform its functions, while a functional or effective medicine can cure an illness. Therefore, when using antonyms for "in-operative," it's essential to choose the word that best describes the desired meaning of the sentence or context.