SYNONYM EXTRACTION APPARATUS, METHOD AND PROGRAM

PROBLEM TO BE SOLVED: To accurately extract a synonym of a word included in the description of a commodity on a site.SOLUTION: A short-term session extraction unit 21 extracts a short-term session for each word. In the whole short-term session, a co-occurrence frequency extraction unit 22 extracts a co-occurrence frequency with a word for each word. An IDF extraction unit 23 extracts a word IDF of each of words having the co-occurrence frequency with a word to be a predetermined value or more, for each word. A synonym output unit 40 outputs words, from among synonym candidates, other than words each of which a word IDF is a threshold or less as a synonym of a word.