- Word stem
Examples The stem of the verb wait is wait: it is the part that is common to all its inflected variants.
- wait (infinitive)
- wait (imperative)
- waits (present, 3rd person, singluar)
- wait (present, other persons and/or plural)
- waited (simple past)
- waited (past participle)
- waiting (progressive)
In linguistics, a stem is a part of a word. The term is used with slightly different meanings.
In one usage, a stem is a form to which affixes can be attached. Thus, in this usage, the English word friendships contains the stem friend, to which the derivational suffix -ship is attached to form a new stem friendship, to which the inflectional suffix -s is attached. In a variant of this usage, the root of the word (in the example, friend) is not counted as a stem.
In a slightly different usage, which is adopted in the remainder of this article, a word has a single stem, namely the part of the word that is common to all its inflected variants. Thus, in this usage, all derivational affixes are part of the stem. For example, the stem of friendships is friendship, to which the inflectional suffix -s is attached.
Stems may be roots, e.g. run, or they may be morphologically complex, as in compound words (cf. the compound nouns meat ball or bottle opener) or words with derivational morphemes (cf. the derived verbs black-en or standard-ize). Thus, the stem of the complex English noun photographer is photo·graph·er, but not photo. For another example, the root of the English verb form destabilized is stabil-, a form of stable that does not occur alone; the stem is de·stabil·ize, which includes the derivational affixes de- and -ize, but not the inflectional past tense suffix -(e)d. That is, a stem is that part of a word that inflectional affixes attach to.
The exact use of the word 'stem' depends on the morphology of the language in question. In Athabaskan linguistics, for example, a verb stem is a root that cannot appear on its own, and that carries the tone of the word. Athabaskan verbs typically have two stems in this analysis, each preceded by prefixes.
Citation forms and bound morphemes
In languages with very little inflection, such as English and Chinese, the stem is usually not distinct from the "normal" form of the word (the lemma, citation or dictionary form). However, in other languages, stems may rarely or never occur on their own. For example, the English verb stem run is indistinguishable from its present tense form (except in the third person singular); but the equivalent Spanish verb stem corr- never appears as such, since it is cited with the infinitive inflection (correr) and always appears in actual speech as a non-finite (infinitive or participle) or conjugated form. Morphemes like Spanish corr- which can't occur on their own in this way, are usually referred to as bound morphemes.
In computational linguistics, a stem is the part of the word that never changes even when morphologically inflected, whilst a lemma is the base form of the verb. For example, given the word "produced", its lemma (linguistics) is "produce", however the stem is "produc": this is because there are words such as production. 
Paradigms and suppletion
A list of all the inflected forms of a stem is called its inflectional paradigm. The paradigm of the adjective tall is given below, and the stem of this adjective is tall.
- tall (positive); taller (comparative); tallest (superlative)
Some paradigms do not make use of the same stem throughout; this phenomenon is called suppletion. An example of a suppletive paradigm is the paradigm for the adjective good: its stem changes from good to the bound morpheme bet-.
- good (positive); better (comparative); best (superlative)
- Lemma (morphology)
- Morphological typology
- Morphology (linguistics)
- Principal parts
- Root (linguistics)
- Stemming algorithms (Computer science)
- Vowel stems
- ^ Geoffrey Sampson; Paul Martin Postal (2005). The 'language instinct' debate. Continuum International Publishing Group. p. 124. ISBN 9780826473851. http://books.google.de/books?id=N0zJNPuXTZMC&pg=PA124&lpg=PA124&dq=%22a+root+is%22+%22a+stem+is%22&source=bl&ots=Amv01e0fmE&sig=p1LNjJBk5iHCDqpf7IDzRKGG3sY&hl=en&ei=bSZmSqCwAYegngOXlJH4Dw&sa=X&oi=book_result&ct=result&resnum=1. Retrieved 2009-07-21.
- ^ Paul Kroeger (2005). Analyzing grammar. Cambridge University Press. p. 248. ISBN 9780521816229. http://books.google.com/books?id=rSglHbBaNyAC&pg=PA248&dq=%22a+stem+is%22+%22a+root+is%22&ei=4CxmSvaCHIqyzQSOg6XpAw&hl=de. Retrieved 2009-07-21.
- ^ http://nltk.sourceforge.net/index.php/Book
- What is a stem? - SIL International, Glossary of Linguistics Terms.
- Bauer, Laurie (2003) Introducing Linguistic Morphology. Georgetown University Press; 2nd edition.
- Williams, Edwin and Anna-Maria DiScullio (1987) On the definition of a word. Cambridge MA, MIT Press.
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