How Latent Semantic Indexing (LSI) Affects Search Engine Rankings

You may be scratching your head wondering what Latent Semantic Indexing is. It can really wreak havoc with search engine rankings and is something every SEO writer should be aware of.

What is Latent Semantic Indexing (LSI)?

Latent Semantic Indexing is basically a language algorithm that examines patterns of words for relational connectivity.

As an example, I'll use a segment I saw on the TV crime show Forensic Files. In this particular episode, the deceased had supposedly left a suicide note. To determine if the note was indeed written by the deceased, a forensic language specialist examined it against known writings of his.

By examining things like syntax, word patterns, use of language, etc., the specialist was able to determine if it was authored by him, or not. She determined that it was not.

Now, she also examined the suspect's known writing samples and determined the suicide note had been written by him, not the deceased.

This is kind of how LSI works. In short, latent semantic indexing allows search engines to figure out what a page is about without matching exact search phrases.

For example, If you write an article about types of apples you eat, by using LSI, the search engines will be able to differentiate it from an article about types of apple computers by the other language surrounding the word "apple."

Ostensibly, an article about apple computers will contain phrases like iMac and computer, while an article about the types of apples you eat wouldn't (ie, because of the relational connectivity between the words).

Why Latent Semantic Indexing Is Important to Making Money Online

In addition to the above, latent semantic indexing goes one step further. Instead of simply evaluating one document independently, LSI looks for relationships between sets of documents.

Eg, if you have a website about SEO marketing, it will scan that website looking for other pages that contain information relevant to that topic. It wouldn't expect to find a page about quilting, for example.

As explained in detail on SEOBook.com: