stemmer

stem1 (stɛm)
—n
1.	the main axis of a plant, which bears the leaves, axillary buds, and flowers and contains a hollow cylinder of vascular tissue
2.	any similar subsidiary structure in such plants that bears a flower, fruit, or leaf
3.	a corresponding structure in algae and fungi
4.	any long slender part, such as the hollow part of a tobacco pipe that lies between the bit and the bowl, or the support between the base and the bowl of a wineglass, goblet, etc
5.	a banana stalk with several bunches attached
6.	the main line of descent or branch of a family
7.	a round pin in some locks on which a socket in the end of a key fits and about which it rotates
8.	any projecting feature of a component: a shank or cylindrical pin or rod, such as the pin that carries the winding knob on a watch
9.	linguistics Compare root the form of a word that remains after removal of all inflectional affixes; the root of a word, esp as occurring together with a thematic element
10.	the main, usually vertical, stroke of a letter or of a musical note such as a minim
11.	electronics the tubular glass section projecting from the base of a light bulb or electronic valve, on which the filament or electrodes are mounted
12.	a.  the main upright timber or structure at the bow of a vessel
	b.  the very forward end of a vessel (esp in the phrase from stem to stern)
—vb (usually foll by from) , stems, stemming, stemmed
13.	to be derived; originate: the instability stems from the war
14.	(tr) to make headway against (a tide, wind, etc)
15.	(tr) to remove or disengage the stem or stems from
16.	(tr) to supply (something) with a stem or stems
[Old English stemn; related to Old Norse stafn stem of a ship, German Stamm tribe, Gothic stōma basis, Latin stāmen thread]
'stemlike1
—adj
'stemmer1
—n

stemmer definition

information science, human language
A program or algorithm which determines the morphological root of a given inflected (or, sometimes, derived) word form -- generally a written word form.
A stemmer for English, for example, should identify the string "cats" (and possibly "catlike", "catty" etc.) as based on the root "cat", and "stemmer", "stemming", "stemmed" as based on "stem".
English stemmers are fairly trivial (with only occasional problems, such as "dries" being the third-person singular present form of the verb "dry", "axes" being the plural of "ax" as well as "axis"); but stemmers become harder to design as the morphology, orthography, and character encoding of the target language becomes more complex. For example, an Italian stemmer is more complex than an English one (because of more possible verb inflections), a Russian one is more complex (more possible noun declensions), a Hebrew one is even more complex (a hairy writing system), and so on.
Stemmers are common elements in query systems, since a user who runs a query on "daffodils" probably cares about documents that contain the word "daffodil" (without the s).
(This dictionary has a rudimentary stemmer which currently (April 1997) handles only conversion of plurals to singulars).
(1997-04-09)