Contents Information retrieval Document Search engine Text units String Non-empty string Token Word token Word Word form Inflected word form Variant word form Word type Normalised word type Normalisation function Term Phrase Text processing Tokenisation Tokeniser Case folding Lemmatisation Stemming Asymmetric query expansion Soundex Consonant Vowel Stop word Term statistics Term frequency Document frequency Usage and meaning Linguistic context Homonym Synonym Thesaurus Contextual similarity Semantic similarity Distributional hypothesis Patterns in text give clues to meaning