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A stemmer is 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”.

Tags: clustering, text data mining