(WAIS, Verity)
``Stemming'' is a technique used to automatically derive variations of a queried word. These variations are then used as part of the search. If stemming is used, then when a data set is indexed, word stems are indexed where possible. For example, "dancing," "danced," and "dancer" would all be indexed as "dance." A question containing the word "dancer", would then turn up documents that may also include "dance", "danced", and "dancing". Two types of stemming are supported: Plural and Porter stemming. Plural stemming attempts to determine the singular form of a word. Porter stemming attempts to find the real base, or stem, of a word and derive any possible alternate variations. The stemming algorithm is selected by the database administrator prior to indexing the database.
See also ``query expansion'' and ``relevance ranking''.