Latent Semantic Index Keywords: A Primer

By Stephanie Logerot | Inbound Marketing Manager

Near the end of last year, I started coming across more and more articles discussing the use of latent semantic index (LSI) keywords when optimizing content for search engines. While the process of latent semantic analysis has been around for a couple of decades, Google has only recently started incorporating LSI keywords into its algorithm. Here, I'll go over the basics and how you can start using LSI keywords to better optimize your content.

1. What is latent semantic indexing?

LSI is a process where an algorithm holistically evaluates pieces of content and determines if and how many words they have in common. Pieces of content that share many words are considered to be semantically similar, and content that doesn't is considered to be semantically different.  An LSI-indexed database applies a numerical value to content based on how semantically similar it is to other content, and returns content it considers relevant to your query.

2. That sounds like gibberish. Explain more.

It's easier to understand if we look at an example. Let's say you want to optimize a web page for the term "dynamometer." Previously, one of the main properties Google used to determine a page's rank was keyword density - basically, how many times a certain keyword appeared on a page. Spammers quickly figured out that this system was easy to game, and they could stuff pages with "dynamometer" every few sentences and have their page rank highly - even if the page had nothing to do with dynamometers.

LSI helps us get around that. Search "dynamometer" in Google and you'll see this in the instant predictions drop-down:

0117_lsiblog.png"Card analysis", "for sale" and "norms" are words Google considers semantically similar to dynamometer. This means that many highly ranked pages for "dynamometer" include these terms. Instead of just showing pages that include the exact term, Google looks for similar terms to help it determine whether a page is relevant to your query.

3. Ok - is that the only way to find LSI keywords?

Nope. The "searches related to" box is another gold mine. For 
dynamometer" we get:


Also, if you have a Google AdWords account, you can use their keyword planner to find LSI keywords. 

If you don't mind rolling up your sleeves and doing some manual (ok, virtual) labor, a great way to find keywords is by searching for your main keyword and then reading through the top results to see which words they have in common. It can be time-consuming, but well worth it if you really need to up your SEO game.

There are a ton of great resources on LSI optimization online. Moz has a great whiteboard Friday video and post where they go into great detail about the process. This post from The Content Wrangler also has some great information. 

Those of us who mainly market to engineers are fairly lucky in that engineers, unlike the majority of the population, will almost always go past the first page of search results to find content related to their search terms. Still, having high-quality, optimized content is the best way to drive traffic to your website. It's worth spending some time learning about LSI keywords and updating your key content to incorporate them. Or, if you'd rather outsource this process, contact us to request a free website audit, and let us help you figure out how to best optimize your site to generate traffic and grow leads.

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Stephanie Logerot

Inbound Marketing Manager