why

Why is a common English interrogative used to request reasons, causes, or purposes behind a fact, event, or action. It appears in questions about causation (Why did the plant die?), explanation (Why is the meeting delayed?), and justification (Why should we adopt this policy?). As a linguistic category, why signals an inquiry into motive, mechanism, or rationale, and it can be answered with a causal account, a functional purpose, or an ethical justification.

Originating in Old English as hwi, related to other Germanic languages such as German warum and Dutch waarom, the word has long served as a general probe into reasons. In modern English it functions as a one-word interrogative that can begin a question (Why is the sky blue?) or be embedded within a sentence (I know why you did it).

In philosophy, "why" raises questions about causation, explanation, and the ultimate reasons for existence. In science, why questions drive inquiry toward causal mechanisms, laws, or models that link phenomena. Distinctions are made between causal explanations (how a process works) and teleological or normative explanations (for what purpose or goal). The classic problem of explaining why there is something rather than nothing has been central to metaphysics; in empirical inquiry, why questions are pursued with hypotheses and evidence, not just speculation.

Practically, asking why promotes understanding and learning but can be difficult to answer definitively. The quality of a "why" answer depends on the availability of evidence, models, and agreed criteria for explanation. In everyday use, why also serves to challenge assumptions and clarify values.