Lemmatizer is the language tool that given any word-form it returns the headword of the morphological lemma this word-form belongs to, e.g. for the word-form κατέστη it returns the headword καθιστώ. In cases where the input word-form belongs to more than one morphological lemmata, the Lemmatizer returns all the corresponding headwords, e.g. for the word-form απαντήσεις it returns απαντώ and απάντηση. The functionality of Neurolingo's Lemmatizer is based on an index that contains all the word-forms of the Morphological Lexicon.
For an extensively inflected language like Modern Greek, the Lemmatizer is an integral functional component of text indexing and searching systems. For example, when the user searches for texts containing the word-form υπολογιστές, he/she would probably like to recall texts that also contain the word-forms υπολογιστής, υπολογιστή and υπολογιστών. In practice, this is achieved by lemmatizing the indexing terms as well as the search terms: texts that contain the word-forms υπολογιστή, υπολογιστές and υπολογιστών will also be indexed with the headword υπολογιστής; a query that contains the word-form υπολογιστές will be expanded with the headword υπολογιστής. This way, a text containing the word-form υπολογιστών can now be associated with a query containing the word-form υπολογιστές through the common headword υπολογιστής.
The Lemmatizer of Neurolingo has been intergrated with the following text indexing and searching systems: