The first large difference is that while fault can be either a noun or a verb, error occurs only as noun. An error is an act or an instance that unintentionally deviates from what is correct or true either in speech or in written form. It also means a moral offense, a sin. In Mathematics, error refers to the difference between the observed and the true value of a quantity. In legal context, error is a mistake in a court proceeding concerning a fact. Fault as noun, refers to an imperfection or the responsibility for a wrongful act. In Geology, it means the break in the continuity in the body of a rock. In Electronics, it refers to some kind of defect caused by poor grounding, for example. In legal context, it means the legal blameworthiness, for example neglect of care, but it implies any negligence defect or judgment.
