What Is LSI?

Despite it’s complicated name, LSI is a simple concept to understand — and a powerful SEO attribute in the eyes of Google.

First, let’s get through the technical specification:

Latent semantic indexing began as a way of matching text. The patent was originally filed on September 15, 1988.

It was designed to predict the meaning of a word by simultaneously analyzing words inside of a document through indexing. Computers would associate the keywords to the search query, compare it to the index, and provide statistically probable search results.

Today, latent semantic indexing has become part of the process that search engines use to organize and classify content.

LSI uses mathematical techniques to find relationships between words and concepts. Semantically related content is further processed and indexed along with directly related content.

It’s important to note that semantic relationships are not the same as being synonymous. Instead, it is a relationship between the words.

For example, suppose you are writing content about art museums. In that case, it would be wise to include keywords about where a museum is located (“art museum dallas”). You might also include that it has virtual tours on its website (“art museum virtual tour”), or that visitors can access the museum’s collection online (“art museum online collection”).

We can express those facts with LSI keywords. These keywords all relate to the primary keyword, “art museum,” but aren’t synonyms—and they are recognized as associated terms by LSI.

In this way, LSI fuels many “long tail keywords” your site may begin ranking for without any conscious effort. It’s an incredibly helpful and powerful tool to have in your SEO toolkit.

 

Is LSI Different From LSA?

You have also heard of LSA (latent semantic analysis), which came into the picture a bit later. It’s an extension of the original LSI framework.

LSI made it possible to process information quickly and determine the relationships between concepts. LSA is based on LSI and also processes natural language.

The theory behind LSA is that processing documents allows for determining the concepts contained in each, by recognizing the general idea. Latent semantic analysis focuses on the meaning of the article or document to draw more accurate conclusions about the relationship between the words.

In plain English: it figures out the “jist” of what’s being said.

Using the relationships proven to exist through LSI and LSA was the beginning of information processing as we recognize it today. Susan Demais, one of the initial researchers and co-authors behind this work, also contributed her knowledge to Microsoft’s search algorithms to further develop and optimize their performance.

 

How Does LSI Work?

LSI removes words that are not pertinent to the phrase or keyword when analyzing a string of words or a query. These words are known as “stop words” and do not affect the overall meaning of the content. Instead, LSI recognizes the association between words that are frequently found together, like Microsoft and Xbox.

Google, for example, takes the remaining words from your search query, and they are then weighed against the Search Quality Evaluator Guidelines document that Google maintains behind the scenes. The document contains user-intent categories including:

  • Visit-in-Person Queries
  • Do Queries
  • Website Queries
  • Know Queries

Understanding the significance behind the user intent allows search engines to define the contextual meaning of a phrase to return the most helpful search results.

Search engines like Google are intelligent and able to identify the meaning behind your words by understanding the relationships that exist in the same context. For example, if your site is about drumsticks, pedals, guitars, and cymbals, LSI is going to associate your site with music.

 

What Makes LSI Important?

In the early days of search engines, crawler bots searched websites for direct uses of primary keywords to help them classify a site’s content.

It was common for sites to repeat a few keywords throughout their content, because keyword density was a significant factor in achieving high rankings. Today, your site can be penalized for using such tactics. Overuse of a keyword is called “keyword stuffing” – and there’s no ‘tried and tested’ number of uses Google considers favorable.

As a result, “keyword density” has been primarily phased out from high performance SEO. A major reason for that is LSI is capable of determining your subject matter regardless – you do not need to signal what your page is about to Google quite as aggressively these days.

As we all know, algorithms are becoming incredibly strong – and they’re intelligent! Purposely inserting your keyword a specific number of times, is more likely to say “Hey Google, here’s exactly what not to rank me for.”

Beginning with Google’s Hummingbird release in 2013, sites that use terms that describe a subject overall receive better rankings because they have richer and more distinctive content.

The more recent update in 2019 involving an AI system named BERT (Bidirectional Encoder Representations from Transformers) affected more than 10% of total search queries. BERT considers the way a single word relates to all words in a phrase. Removing a single word impacts how the search results come back.

These semantic words that BERT also recognizes, further contribute to each query’s unique context. A key difference is that BERT looks at words that occur before and after each word in a query, where LSI removes the “stop words.”

Keeping both BERT and LSI in mind, your content will stand out from what’s on a competitor’s website if you use semantic keywords. Using richer keywords allows viewers to learn more about you, your business, and what you offer.

 

Should Marketers Incorporate LSI?

You’ll find two schools of thought regarding latent semantic indexing. Some say that LSI is critical to your content, while others say it isn’t helpful at all. The truth is that regardless of your viewpoint, taking LSI into account can still strengthen your online visibility.

Synonyms and variants are essential in your web copy to ensure optimization. The reasoning behind this is that not everyone is going to search for the same phrase. For example, if you want to find a pool repair person in Ohio, you might have a few different ways to search:

  • Ohio pool repair
  • Pool repairman in Ohio
  • Get my pool repaired in Ohio

There are several other possibilities, but you get the point. The application of LSI can help you create phrases that will assist search engines when indexing your site.

Incorporating latent semantic indexing makes it easier for search engines to pull information and return search results that fit what your potential client is looking for. You still need to write with an authoritative tone, but including LSI in your content helps customers find the solution you provide.

 

What Are the Benefits of Using Latent Semantic Indexing?

One of the most significant benefits of using latent semantic indexing is the prevention of being singled out as spam. Variants increase your site’s credibility, and your user is likely to have a better experience when they search your website. In a way, LSI is the antithesis of keyword stuffing.

Bounce rates are also reduced by using LSI keywords. These types of keywords give your website more depth and is, therefore less likely to be categorized incorrectly. It’s a subtle correlation, but the concept is that you will have less ‘junk visitors’ (visitor’s who had a search query somewhat related to your content, quickly realize it’s not what they’re searching for, and quickly leave).

LSI keywords also sound more natural when they’re on your site. When words flow, your audience is more likely to stay on your website because they find it easy to engage with meaningful. Your website naturally improves its ranking because the search engines understand your website better, too.

We’ve all read those “Top 10 lists” that use their target keyword way too much. They go something like this:

“Hey Eggplant Lovers! Joey Egglant here with another riveting piece of content for all your eggplant loving needs. Here are the Top 10 eggplants for your eggplant-indulging pleasure.”

Can you guess what the focus keyword was? 😉

Well, so can the algorithm. And like people, they do not usually react well when they feel they are being manipulated.

 

How Do You Use LSI Keywords?

You want to add appropriate LSI keywords throughout your site, but it must be natural to be effective.

Don’t overdo it with any specific word, so you want to keep the number of individual variation occurrences to a minimum. Use each LSI phrase once per page, and incorporate multiple variants for best performance. Essentially, the best example of latent semantic indexing is an essay or lecture. You do not continually repeat the topic of your essay. You find synonyms, adjacent phrases, and often do this naturally. To constantly reiterate the entire essay topic would feel unatural.

To go back to our example, if your content is a blog post titled “The History of Eggplants,” you don’t want to beat this exact phrase into the ground. Semantic choices mightinclude “eggplant history,” “prior eggplant harvesting methods,” or “recent eggplant developments.” The core topic is still history, and you have more than one way to reference that (as you would when speaking to another person). In short, the answer to adding latent semantic indexing to your pages is to speak for a human (not a search engine).

There are tools being developed as well, such as LSI keyword generators and WordPress plugins. However, these can lead to mixed results. When in doubt, ask yourself, “would a person say it this way to me?” That’s what Google is checking for too. It doesn’t look favorably upon people trying to ‘game the algorithm,’ which is exactly what hammering home the same exact keyphrase will do. In another time, this was a quick way to get some bonus points with a search engine. These days, Google knows the difference.

That’s the primary goal of incorporating latent semantic indexing into the process. As we all know, repeating yourself over and over does not help people understand you! So why would we accept it from our articles?

LSI Is an Indexing and Retrieval Method

The bottom line is that LSI helps us find stuff on the internet. It improves the searching experience by deciding if certain words are related, giving us better search results. You can search for physicians or doctors near you, and they’ll both come back with similar results. LSI makes this understanding possible because those words often occur with other words like “hospital” or “patient.”

Latent semantic indexing is still critical in SEO today. By incorporating LSI keywords into your content, your SEO naturally improves, organically improving your search engine ranking.

Better rankings mean more people are going to see your site. If you set your site up to feel pleasant for your customers, they’ll stay on your website longer (and be more likely to convert).

Use semantic keyphrases correctly, and you’ll see improvements to your site traffic.