Lemmatization

Lemmatization maps inflected word forms to their canonical dictionary form — the lemma — using linguistic knowledge of morphology and part-of-speech. Unlike stemming, it preserves valid words: 'better' lemmatizes to 'good', and 'ran' to 'run'. Lemmatization is more accurate than stemming but requires a lexicon and part-of-speech disambiguation, making it slower and more language-specific. It improves vocabulary consistency in downstream NLP tasks such as classification and information extraction.