What is Latent Semantic Indexing (LSI) and does Google use it?


Latent Semantic Indexing (LSI) sounds like something straight out of a science fiction film or an advanced computer science curriculum, right? Well no, it is actually an internet marketing concept that, according to the SEO experts, “helps” you avoid the hassle of constantly looking for the most affordable SEO service for your website keyword optimization strategy. But is LSI the key to success in online businesses?

The term LSI has become a sort of a buzzword in the SEO industry, partly because of famous influencers and SEO power users. They claim that using LSI will result in an overall better ranking on SERPs. The term has become so popular in fact, that a Google search for LSI will result in several good quality websites claiming that using LSI will organically boost your website’s performance.

This article lays the groundwork for the aforementioned understanding and will attempt to debunk the various myths and misinformation regarding LSI and its actual resourcefulness. We will also provide alternative methods to rank better in the SERPs. Lastly, we will throw light on the famous myth that LSI advocates have consistently vouched for in their arguments, that “Google also uses LSI for their search engine operations”.

What is Latent Semantic Indexing?

To put it in more technical terms, latent semantic indexing, also termed as latent semantic analysis, is a mathematical procedure developed in the late 80s to enhance the precision of informational retrieval between networks that were running during that time. LSI uses a procedure called singular value decomposition (SVD) that analyzes unstructured data within documents (web files) to identify patterns and relationships between the contained data.

Let us just define these words:

  • Latent – hidden or inactive.
  • Semantics – the study of words.
  • Index – understanding, and organization.

LSI finds the latent relationships between the semantics contained within a web file in order to index the information more effectively. It was an innovative step at that time since it created a bridge to understand the contextual nature of the words used in the documents. Previously, the technologies used were not so effective in using synonyms to understand natural language use and the change in the context of the documents with regards to the situation. An example of this is that the words “hot” and “dog” have totally different contextual meanings if used separately. However, when combined they have a different meaning altogether and a pretty delicious fast food meal.

Because machines had difficulties in understanding and adapting to changes in context, LSI became the hero and provided innovation in understanding semantics that no other technology previously had the ability to.

As the web was not as sophisticated as it is today, LSI proved useful in indexing small sets of documents and static web files in the 80s. It clustered together with the commonalities in themes in documents, which proved extremely useful for early search engines.

In a timeline, LSI can be summarized as follows:

  • Developed in the late 80s for the purpose of information retrieval. Its conception came about as a result of earlier technologies failing to understand the concepts of synonyms and polysemy.
  • It created a specific approach to understanding the hidden structures and contexts in language.
  • It provided indexing for categories in which certain concepts fall.
  • Worked perfectly on small static documents.

Latent Semantic Indexing & SEO

Now that we have understood the history of LSI, it only makes logical sense that LSI would allow search engines to understand synonyms and that using synonyms throughout the whole document could, in retrospect help search engines understand your content better. Additionally, it can also allow search engines to index your files in a much more effective manner. Therefore, it is only logical that using synonyms to enhance the thematic relevance of your content will result in a better SEO right? It is true that it helped make indexing better in the late 1980s, but there is no proof that the same case holds true in recent times.

Nonetheless, modern-day advocates of LSI have argued extensively that LSI is being used by Google in their search engines. The paths of Google and LSI have crossed way too many times, but in fact, there is a logical explanation as to why LSI and Google are correlated, even when they are not.

Google’s internal systems are based on the study of semantics which is a fundamental tool in the SEO industry. Google’s entire semantic system for document indexing and information retrieval is too advanced and evolved as compared with LSI.

In order to make search engines work for us, we need to structure and label our data clearly, so that our content does not get lost in the dreaded second-page results of Google search. We need to understand the concept of concurrence which is the identification of keywords that are grouped together to form a contextual meaning. We can easily identify the keywords by researching products and services related to our business and include accurate terminologies on our site’s content.

This is generally a much more productive and clearer approach than filling your content up with useless synonyms that jumbles up the content and scares away the readership.

LSI is pretty much useless

We have gone at length about the innovations in information retrieval and indexing that LSI brought in the late 1980s, but let us all be logical here and realize that we use practically no technology from the 1980s in 2018. So yeah, LSI has no use in 2018.

It is true that search engines are naturally in the business of information indexing and retrieval, but saying that Google uses LSI without any evidence is just flawed reasoning.

But synonyms will not do much harm to your website, right? So adding them is not that big of a deal and it might even work out for your SEO strategy, right? You are welcome to try such a technique. Because there is no proof that Google does not use LSI, there is no proof that this will work or not.

The counterargument by the advocates run in like this: “many activities fall into the same category”. But that does not mean that there is a direct link between the two. This argument follows the same logic that if Google allows a better ranking on SERPs for using the Comic Sans font, then it should be tried regardless of the fact that it makes your content and your whole website look irrelevant and childish. A word of advice: never use Comic Sans.

If you look at it from a non-technical webmaster’s perspective, using LSI might sound like an intuitive approach particularly because of its scientific name. However, its actual application is not really scientific. It is just the addition of synonyms and related keywords, which is pretty much child’s play. It is much more intuitive to indulge in actual research regarding the entire field of semantic indexing rather than blindly chasing internet blogs that offer this “one simple trick to rank better on SERP’s”.

As discussed before, having a clear and structured data for indexing and using the concept of concurrence will benefit you better in the long run and provide your content with much more value than LSI terms.

Google Patents & LSI

The final phase of this discussion will lay down some basic facts regarding Google and its use of LSI. This whole comparison has been the topic of serious debate in the realm of web technologies.

To put it simply, Google does not have a patent related to LSI, nor do they have any sub-patent that lists LSI as being used previously in any technology. In reality, none of Google’s listed patents have had a direct relationship with the word “LSI”, but they have discussed phrase concurrence and semantics.  You can see for yourself at www.google.com/patents.


Internet blogs and LSI “activists” have misled the general population and some intellectuals on the concept of LSI. In order to create better, more informed SEO professionals, we need to focus on building a community that gives importance to evidence-based findings rather than internet click-bait. Promotion of obsolete technologies will not do much damage in the short run but it will erode trust in the long run.