Description:
LSI (Latent Semantic Indexing) is an indexing and retrieval technique that uses a mathematical formula to identify patterns in any given paragraph of text. It helps Google better understand what the content is about and how relevant it is to the search query. LSI is one of the important ranking factor that Google takes into consideration.
https://www.imediadesigns.ca/2017/05/08/what-is-lsi-and-how-to-use-it-for-seo/