Vague expressions are omnipresent in natural language. As such, their use in legal texts is virtually inevitable. If a law contains vague terms, the question whether it applies to a particular case often lacks a clear answer. One of the fundamental pillars of the rule of law is legal certainty. The determinacy of the law enables people to use it as a guide and places judges in the position to decide impartially. Vagueness poses a threat to these ideals. In borderline cases, the law seems to be indeterminate and thus incapable of serving its core rule of law value. In the philosophy of language, vagueness has become one of the hottest topics of the last two decades. Linguists and philosophers have investigated what distinguishes "soritical " vagueness from other kinds of linguistic indeterminacy, such as ambiguity, generality, open texture, and family resemblance concepts. There is a vast literature that discusses the logical, semantic, pragmatic, and epistemic aspects of these phenomena.