1. A program storage device encoded with machine-readable computer program code for document categorization, the storage device including instructions for causing a computer to implement a method comprising: identifying with the computer terms occurring in a collection of documents; determining a cohesion score for each of the terms, the cohesion score is a function of a cosine difference between each of the documents containing the term and a centroid of all the documents containing the term; sorting the terms based on the cohesion scores; creating categories based on the cohesion scores of the terms, wherein each of the categories includes only documents (i) containing a selected one of the terms and (ii) that have not already been assigned to a category; and moving each of the documents to a category of a nearest centroid, thereby refining the categories; wherein creating the categories, comprises: (a) selecting the term with the highest of the cohesion scores that has not been selected; (b) if a number of the documents that are uncategorized contain the term selected as having the highest of the cohesion scores is greater than a minimum category size, creating another category consisting of all documents that contain the term selected as having the highest of the cohesion scores when the number of documents that are uncategorized contain the term selected as having the highest of the cohesion scores is greater than a minimum category size; (c) ceasing creating the categories when the number of the documents that are uncategorized is less than an uncategorized document size or when the number of the other categories created is greater than a maximum number of categories; and (d) repeating steps (a)-(c) until step (c) is performed or none of the terms remain when, at least one of, (i) the number of the documents that are uncategorized is not less than the uncategorized document size and (ii) the number of the other categories created is not greater than maximum number of categories.