1. A computing system, comprising: a storage to store: sets of words, wherein each set is associated with a category; and a processor to: determine difference distances between the words within each of the individual categories; select a difference distance threshold for each of the categories based on the difference distances for the particular category; associate a category with a target word, comprising: determine difference distances of the target word to the set of words of each of the categories; and determine whether one of the difference distances of the target word is below a threshold associated with the category; and output the category if the difference distance of the target word is below the threshold.