The increasing use of keyword density has paved way for the powerful LSI(Latent Semantic Indexing). LSI helps GOOGle, the search engine giant to distinguish the web pages having the keywords repeated several times in them from the web pages having the keywords that relates well with each other. LSI conceives natural & synonymous relationship between words.
Google thought it is of utmost necessity to incorporate LSI technology to decide on the keyword ranking. Google purchased the LSI technology from Applied Semantics. The same technology powers Adsense which works on contextual targeting.
Quintura tools assists Search Marketers for finding out related keywords for their target keywords.