What is the Latent Semantic Indexing?

Latent Semantic Indexing (LSI) is a form of information retrieval to understand the relationship between words. Academically, this is often called Latent Semantic Analysis instead of indexing.

In the industry of search engine optimisation, we often use the term LSI to mean other words that say the same thing. However, a more academic definition would be terms that are semantically related, not just similar.

For example, these terms are all related but do not mean the same thing:

  • Hospital
  • Doctor
  • Nurse
  • Ambulance
  • Patient

Some tools use related queries and associated topics instead of words. While these sometimes include LSI terms, they are not quite the same thing. One example of this type of tool is LSIGraph.

Front Page of LSI Graph Keyword Generator

How can I check for Latent Semantic Indexing?

There are very few tools that use proper forms of Latent Semantic Indexing. Due to the necessary processing and large corpus, this is often unachievable.

However, search engines such as Google already own lots of powerful computers and servers. Since they already crawl the web for pages, they also have a large corpus of documents to compare.

To check for your LSI terms, you may wish to use free tools such as Wordcounter on your competition. This tool will show you the most commonly used words for that page. Through manual checking, you can quickly pick up related terms.

Using Wordcounter for TF-IDF

How can I improve Latent Semantic Indexing for my website?

The best way to improve Latent Semantic Indexing is to create meaningful content that is concise and interesting. Avoid repetition and look for the terms that you haven’t mentioned.

While synonyms can be useful in this regard, it may be worthwhile to read your competition’s content. This process can give you a good idea of the type of information that Google serves its users.

Two useful tools for finding related words are the online Thesaurus and Dictionary. These tools can help in discovering words within the same field that inspire your content.

All of these are part of keyword research for your website.

Using a Thesaurus for Keyword Research