LSI Keywords- Latent Semantic Indexing keywords are words that are related semantically to your primary keyword. LSI keywords are not necessarily synonyms, they are simply words that cluster with other words because they share a certain context. LSI keywords are words that have been found, by the search engines, to cluster together. Latent Semantic Indexing is like a search engine saying to itself: “If I find this keyword on a particular page, I am also likely to find these other keywords”.