Grey literature can be defined as, “that which is produced by government, academics, business, and industries, both in print and electronic formats, but which is not controlled by commercial publishing interests and where publishing is not the primary activity of the organization.”
Conference papers, presentations, technical reports, Theses and dissertations, government publications, research synopsis, which are not published through commercial channels are some examples of grey literature.
Dear Sir,
The Grey Literature consist with documentary material in print and electronic formats, such as reports, preprints, internal documents (memoranda, newsletters, market surveys, etc.), theses and dissertations, conference proceedings, technical specifications and standards, trade literature, etc. These are not readily available through regular market because it was never commercially published. Such works pose challenges to libraries in identification (indexing is often limited) and acquisition (availability may be uncertain). Absence of editorial control also raises questions of authenticity and reliability. Alternative methods of supply and bibliographic control have evolved in response to the need to preserve and provide access to such material.
Synonym: semipublished.
In simple words:
Grey literature (or gray literature) is a term used for scientific and technical reports, government documents, theses, patent documents, unpublished materials and etc. which are difficult to obtain or findout. In the modern context this term is using by librarians, academicians, etc.