The dropping of characters and the addition of a symbol at the end, beginning, or within a word in a keywords search to retrieve variant forms. Truncation is particularly useful in retrieving the singular and plural forms of a word in the same search.

Example: *librar* to retrieve records containing "interlibrary," "intralibrary," "librarian," "librariana," "librarianship," "libraries," "library," etc.

In most online catalogs and bibliographic databases, the end truncation symbol is the * (asterisk), but since the truncation symbol is not standardized, other symbols may be used (?, $, #, +). In some search software, the user may add a number after the symbol to specify how many characters the symbol may represent (example: facet?1 to retrieve "facets" but not "faceted" or "facetiae").

As a general rule, it is unwise to truncate fewer than four characters (example: art* retrieves "artist," "artistic," "artistry," and "artwork" but also "artichoke," "artillery," etc.). Some databases are designed to truncate automatically. Searchers are advised to read carefully any help screens before truncating in an unfamiliar database. Synonymous with character masking.

See also: wildcard.

From ODLIS, Online Dictionary for Libary and Information Science by Joan M. Reitz
http://lu.com/odlis/about.cfm