Nonvalid is often used to indicate something that lacks validity or truthfulness. Its antonyms are words that describe the opposite of nonvalid. The first antonym for nonvalid is valid, which means something that is based on truth and facts. Another antonym for nonvalid is genuine, which refers to something that is authentic, real or sincere. Other potential antonyms for nonvalid include authentic, credible, dependable, honest, lawful, legitimate, reliable, and truthful. Using an antonym for nonvalid can help to provide context and clarity to a statement, especially when one wants to emphasize that something is true or trustworthy.