Word sense disambiguation (WSD) is the task of selecting the correct sense for a word. WSD algorithms take as input a word in context and a fixed inventory of potential word senses and outputs the correct word sense in context.

• In some situations, we just need to disambiguate a small number of words. In such lexical sample tasks, we have a small pre-selected set of target words and an inventory of senses for each word from some lexicon. Since the set of words and the set of senses are small, simple supervised classification approaches work very well.
• More commonly, however, we have a harder problem in which we have to disambiguate all the words in some text. In this all-words task, the system is given an entire texts and a lexicon with an inventory of senses for each entry and we have to disambiguate every word in the text (or sometimes just every content word).