The notion of a “lemma”

The notion of alemmais so familiar in corpus linguistics that it scarcely needs a formal definition. When a wordlist or a text is lemmatised, the process is apparently transparent, so that any observer can understand how the lemma relates to the original set or string of words. We shall argue in this paper that, on the contrary, the concept of lemma is not well defined, and is in need of a clear formal definition. The lemma is a fundamental concept in the processing of texts in at least some languages, a point we shall illustrate with respect to Arabic and Malay. It so happens that English lemmas are not typical of the general category, so that linguists who base their understanding of the lemma on English obtain a distorted view. It is essential to reverse the direction of argument, and to start with a general understanding of the lemma, and to consider English lemmas in the wider context.