LSI, which stands for latent semantic indexing, is a part of the Google algorithm which aids the search engine in supplying the greatest search results feasible. When content writers realize what LSI is, they can take advantage of the process in order to rank their optimized pages better in the search results.
Latent Semantic Indexing permits Google to associate comparable words which can be related to a specific topic. For example, if a page is about “dog arthritis” and optimized for that term, there may possibly really well be other words on the page such as canine, joint disease, glucosamine, limping, osteoarthritis, hip dysplasia, etc.
The search engine has seen this pattern on enough pages that they now know to connect those words with the overall topic of “dog arthritis”. Seeing those words on the page along with the primary keyword gives Google far more confidence in ranking the page well for the optimized term.