1, 2. Investigation, examination, inquiry, research express the idea of an active effort to find out something. An investigation is a systematic, minute, and thorough attempt to learn the facts about something complex or hidden; it is often formal and official: an investigation of a bank failure. An examination is an orderly attempt to obtain information about or to make a test of something, often something presented for observation: a physical examination. An inquiry is an investigation made by asking questions rather than by inspection, or by study of available evidence: an inquiry into a proposed bond issue. Research is careful and sustained investigation.

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