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A Mathematical Model for Context and Word-Meaning To appear in Fourth International and Interdisciplinary Conference on Modeling and Using Context, Stanford, California, June 23-25, 2003 Dominic Widdows Center for the Study of Language and Information, Stanford University dwiddows@csli.stanford.edu ∗ April 8, 2003 Abstract Context is vital for deciding which of the possible senses of a word is being used in a particular situation, a task known as disambiguation. Motivated by a survey of disambiguation techniques in natural language processing, this paper presents a mathematical model describing the rela- tionship between words, meanings and contexts, giving examples of how context-groups can be used to distinguish different senses of ambiguous words. Many aspects of this model have interesting similarities with quan- tum theory. 1 Introduction Context plays a key role in determining the meaning of words — in some con- texts the word suit will refer to an item of clothing, in others a legal action, and so on. In the past decade, the challenge of incorporating contextual models into the way information is described has become very immediate and practical, in the wake of rapid technological advances. To compare and combine information which is readily available but varies across languages, domains of expertise and media, it is important to have some way of expressing what that information actually means in a common and flexible framework. Context can be very useful here — if someone is trying to buy a new computer they will be much more interested in the term PC if it occurs in a