The word "bat" can denote an animal, a sports apparatus, the blink of an eye, or more. While humans can select the appropriate meanings when hearing such words, Internet keyword searches and machine translations demonstrate that computers all too often fail at the process of Word Sense Disambiguation (WSD). This book provides an overview of the field, descriptions of novel research, accounts of previous approaches and methodologies, and an evaluation of a practical computer system that has been found to produce accurate disambiguation decisions in English.