What Is Latent Semantic Indexing?

A search engine has two functions. The first is to understand content – to look at a page and “see” what it’s talking about. The second is to understand search intent – to understand what you’re looking for when you do a search, and on a more advanced level, to understand the difference between “apple” the fruit and “Apple” the company. Search engines use incredibly complex algorithms to match intent with content, and they’re mostly pretty good at it, but they still have some flaws in their programming.

One big flaw is that algorithms can’t understand context in the way that a human being can (yet.) For example: if I’m writing an article about about the “Nintendo Switch” using words like “console,” “controller,” and “framerates,” every person reading it knows that this writing pertains to videogames even if I never actually use the word “videogames” in the article. However, if a search engine is looking for the keyword “videogames,” it might not realize that it should bring up my article for a search on that topic.

That’s where Latent Semantic Indexing comes in. Search engines use this technique to look not only for the primary keyword in the search, but also for secondary keywords that it has learned are relevant. To continue the example from earlier, a search for “videogames” might also bring up any article that mentions “consoles” or “controllers” or “E3.” These are known as “LSI keywords,” and they’re a hugely important part of any modern marketer’s job.

Why Is LSI Important?

There’s lots of things that are great about LSI. It helps search engines provide more detailed and relevant search results, which in turn helps the users of search engines more easily find the content they were looking for. And from our perspectives – the perspective of the marketers and publishers and content creators who want their site to be found amidst the endless detritus of the Internet – LSI brings us a more engaged audience by connecting us with users who are interested in our specific content. It also means that we can increase our search rankings by making sure we’re using LSI keywords and best practices.

What Do I Need To Do About LSI?

Well, you could always let Kiai do it for you. But as a general rule, you need to understand the LSI keywords that relate to your content and make sure you’re using those on your page. There’s a lot of tools out there that will help you find these keywords, with varying degrees of actual usefulness – the simplest is to just type the primary keyword of your article into Google and see what related searches pop up. Often, good LSI keywords will include more specific variations on the original phrase – “videogame news,” for example, or “PC videogames.” Consider what people who use these keywords are looking for. Is your site a games retailer? Then “used videogames” might be a phrase that’s important to use in your copy, while you shouldn’t deceive searchers by including something like “videogame reviews.” If you’re a games journalist, the opposite would be true.

So, while Latent Semantic Indexing may sound scary, it’s pretty intuitive if you’re already following best SEO practices. After all, we very rarely use the exact same word to refer to an idea over and over again (unless you’re keyword stuffing, which you should never be doing anyway.) The key is to make sure that you’re including the right LSI keywords to bring people to your content, and to make sure that you’re putting those keywords in every part of your page (meta descriptions, permalinks, headers, etc.)

Also published on Medium.