Why is different from other wh-phrases in that it does not occur in a multiple whquestion. Syntactic explanations have been given for it, but this paper tries to give a semantic explanation to it. A semantically anomalous sentence need not be rejected by syntax. If multiple wh-questions with why are semantically anomalous, they cannot be evidence for any syntactic rule. Section 1 gives the basic assumptions, Section 2 clarifies the semantics of why which underlies its syntactic behavior. Section 3 compares why with naze in Japanese, and discusses Wh-Merger, which applies in Japanese but not in English
