A number of compound terms use grey to signify something which is part-way between the extremes of formality and informality or legality and illegality. Two which are well established are grey economy, commercial activity which is not recorded in official statistics but which isn’t actually illegal, and grey market, informal channels of trading, unsanctioned by manufacturers or regulators. (The terms grey power and grey pound are not part of this set, as both use grey in the sense of grey-haired in reference to the economic and social strengths of older people.)
The term grey literature refers to a wide range of types of informational material which is made available to the general public by public and private sector organisations whose function is not primarily publishing. Such information includes reports, brochures, guides, dissertations, product information, budgetary data, memoranda, and research findings. A more formal definition is: “That which is produced on all levels of government, academia, business and industry in print and electronic formats, but which is not controlled by commercial publishers”.
The key difference between other sorts of publishing and grey literature is that the latter is not produced as a commercial undertaking, but as part of a communications process. There have so far been two international conferences dealing with grey literature, with a third scheduled for Autumn 1999, and the term is becoming established in information science.