9. The apparatus as recited in claim 6 , wherein the filter module is further configured to retain another word of the one or more words which frequencies of appearance vary across the plurality of categories at an amount greater than the first variation threshold.
6. An apparatus comprising: one or more processors; memory; a parsing module stored in the memory and executable by the one or more processors that parses a text into one or more words; a filter module stored in the memory and executable by the one or more processors that filters the one or more words to provide one or more filtered words prior to classification of the text, wherein the filter module filters a word of the one or more words which frequencies of appearance vary across a plurality of categories at an amount less than a first variation threshold and greater than a second variation threshold, the second variation threshold being greater than zero; a query module stored in the memory and executable by the one or more processors that determines a word vector in a pre-constructed spherical space model for each filtered word of the one or more filtered words, a number of dimensions of the spherical space model being equal to a number of the plurality of categories; a calculation module stored in the memory and executable by the one or more processors that determines a distance between a sum of word vectors of the one or more filtered words and a respective category vector for each category, and accumulates normalized word frequency values of the one or more filtered words to obtain a normalized word vector sum; and a classification module stored in the memory and executable by the one or more processors that classifies the text into one or more categories based on the determined distance of each category, the one or more categories corresponding to a largest component of the normalized word vector sum.