Latent Semantic Analysis (LSA) is applied by taking millions of web pages, where the search engines can learn which words are related and which noun concepts relate to one another. Searh Engines are considering related terms and recognizing which terms that frequently occur together, maybe on the same page, or in close enough proximity. So it is mainly used for language modeling or most other applications.
Latent Semantic Indexing and Search Engines Optimimization (SEO)
The closest search engines have come to actual applications of this technology so far is know as “Associative Indexing” and it is put in effect under Stemming, or the indexing of words on the basis of their uninflected roots (plurals, advers, and adjectival forms are reduced to simplified noun and verb forms before indexing).