Which word describes something that is not genuine or not valid?

The term "spurious" is used to describe something that is not genuine or not valid. It often refers to things that are deceitful in appearance or nature, lacking authenticity, or being false. For instance, a spurious claim could be one that is unsubstantiated or falsified, misleading people into believing something that is untrue. This word captures the essence of something that misrepresents itself or originates from an illegitimate source.

In contrast, the other words do not convey the same meaning. "Rudiment" refers to the basic principles or elements of a subject, often used in educational contexts. "Unremitting" describes something that is relentless or ceaseless, indicating continuity without interruption. "Gratuitous" typically refers to something that is uncalled for or unwarranted, often implying a lack of necessity. None of these alternatives represents the idea of being false or invalid as effectively as "spurious" does.