BioLemmatizer
Lemmatization tool for morphological analysis of biomedical literature
...It focuses on the inflectional morphology of English, including the plural form of nouns, the conjugations of verbs, and the comparative and superlative form of adjectives and adverbs.
README: https://sourceforge.net/projects/biolemmatizer/files/
The BioLemmatizer 1.2 release adds an optional functionality to normalize British English spellings into American English spellings and then retrieve corresponding lemmas.
If you use the BioLemmatizer to support academic research, please cite the following paper:
Haibin Liu, Tom Christiansen, William A Baumgartner Jr, and Karin Verspoor BioLemmatizer: a lemmatization tool for morphological processing of biomedical text Journal of Biomedical Semantics 2012, 3:3.