16. The system of claim 15 , wherein the processor further comprises: an associated score calculation module configured to numerically express, as an associated score, the association between the associated keyword or the extended keyword and the other keywords based on the association indicator; and a ranking score calculation module configured to calculate a ranking score for each purpose of usage based on the associated score and the independent indicator, wherein the search module is configured to provide, based on the ranking score, the associated keyword or the extended keyword with respect to the search word, 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.
16. The system of claim 15 , wherein the processor further comprises: an associated score calculation module configured to numerically express, as an associated score, the association between the associated keyword or the extended keyword and the other keywords based on the association indicator; and a ranking score calculation module configured to calculate a ranking score for each purpose of usage based on the associated score and the independent indicator, wherein the search module is configured to provide, based on the ranking score, the associated keyword or the extended keyword with respect to the search word, 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. 23. The system of claim 16 , wherein the ranking score calculation module calculates the ranking score by adding a sum total of values calculated by applying an individual weight to the independent indicator, and a value calculated by applying a weight corresponding to the purpose of usage to the associated score.