Encyclopædia Britannica, 15th ion: volumes of the Propedia (green), Micropedia (red), Macropedia (black), and 2-volume Index (blue)
A reference work is a work, such as a book or periodical (or their electronic equivalents), to which one can refer for information. The information is intended to be found quickly when needed. Such works are usually referred to for particular pieces of information, rather than read beginning to end. The writing style used in these works is informative; the authors avoid use of the first person, and emphasize facts.
Indices are a common navigation feature in many types of reference works. Many reference works are compiled by a team of contributors whose work is coordinated by one or more ors, rather than by an individual author. Updated ions are usually published as needed, in some cases annually (Whitaker's Almanack, Who's Who).
In contrast to books that are loaned, a reference book or reference-only book in a library is one that may only be used in the library and may not be borrowed from the library. Many such books are reference works (in the first sense), which are, usually, used briefly or photocopied from, and therefore, do not need to be borrowed. Keeping reference books in the library assures that they will always be available for use on demand. Some reference-only books are too valuable to permit borrowers to take them out. Reference-only items may be shelved in a reference collection located separately from circulating items. Some libraries consist entirely, or to a large extent, of books which may not be borrowed.
Types of reference work
These are the main types and categories of reference work:
Abstracting journal – a published summary of articles, theses, reviews, conference proceedings etc. arranged systematically
Almanac – an annual publication listing a set of current, general or specific, information about one or multiple subjects
Annals – concise historical record in which events are arranged chronologically
Atlas – a collection of maps traditionally been bound into book form
Bibliography – a systematic list of books and other works such as journal articles on a given subject or which satisfy particular criteria