The term sourcebook (or source book) is used to describe many different kinds of books such as collections of core articles (i.e., anthology), bibliographies, biographies, printed archival sources, directories and so on. There seems to be no consensus in the application of this term.
In American universities, a sourcebook, either a standard one or a custom collection, may function as a supplement or replacement for a textbook.
In American law schools, casebooks are similar to sourcebooks, offering selections of legal cases and commentary, forming the basis for analysis and discussion.
In games a sourcebook is a publication intended to supplement the core materials of a gaming product. Sourcebooks are most commonly used to complement role-playing games and some tabletop or wargaming series, and often contain optional rules, scenarios, or other materials that players can use to extend or enhance the central game.
Popular gaming series with many sourcebooks include: