Invalid is a term used to describe something that is not legally or officially recognized. Antonyms of the word invalid include legitimate, valid, authentic, legal, accurate, and justified. A valid document, for instance, can be contrasted with an invalid document that does not meet the required specifications. A person's valid argument that is supported by facts can be contrasted with an invalid argument that lacks coherence and substance. In daily interactions, people can use antonyms of invalid to express opposing meanings regarding an issue. Therefore, it is essential to have antonyms to invalid as they serve as a reference point to express valid and non-valid situations.