40. The method of claim 39 , further comprising: numerically expressing, as an associated score, the association between the associated keyword or the extended keyword and the other keywords based on the association indicator; and calculating a ranking score for each purpose of usage based on the associated score and the independent indicator, wherein providing the associated keyword or the extended keyword with respect to the keyword comprises providing the associated keyword or the extended keyword with respect to the search word, based on the ranking score, the association indicator comprises at least one of a purchase association indicator, an advertising association indicator, a service data association indicator, an exposure association indicator, a subject context association indicator, a knowledge shopping association indicator, and a duplication indicator of each association indicator, and the independent indicator comprises a plurality of indicators including at least one of a common indicator, a cost per click (CPC) indicator, and a cost per mille (CPM) indicator.
40. The method of claim 39 , further comprising: numerically expressing, as an associated score, the association between the associated keyword or the extended keyword and the other keywords based on the association indicator; and calculating a ranking score for each purpose of usage based on the associated score and the independent indicator, wherein providing the associated keyword or the extended keyword with respect to the keyword comprises providing the associated keyword or the extended keyword with respect to the search word, based on the ranking score, the association indicator comprises at least one of a purchase association indicator, an advertising association indicator, a service data association indicator, an exposure association indicator, a subject context association indicator, a knowledge shopping association indicator, and a duplication indicator of each association indicator, and the independent indicator comprises a plurality of indicators including at least one of a common indicator, a cost per click (CPC) indicator, and a cost per mille (CPM) indicator. 41. The method of claim 40 , wherein numerically expressing the association as the associated score comprises calculating a single associated score by applying an individual weight to the association indicator.