Understanding LSI To Help You Rank Better

April 9, 2009 · Filed Under google, On Page SEO, SEO Advice, SEO Tips · 3 Comments

I thought I’d take a moment to explain to you what LSI is and why it’s important to your overall SEO efforts.

A lot of people it seems are very confused about how LSI fits into their overall SEO plan or even what it is.

LSI stands for Latent Semantic Indexing and while a very large and complicated phrase, it really means nothing more than using “related words and phrases” throughout your content.

Let’s take an example.

Let’s say that you were writing a web page on the topic of “iPhones”. As you’re writing this content, you might naturally use related words and phrases such as “Mac”, “Apple”, “computer”, “cell phone”, etc.

That’s where LSI comes into play. All of those related words, those semantically related words relate to the overall topic of that web page. It is not the same thing as the plural of a word, LSI means the “semantically” related word or phrase plurals are simply “more than one”.

And Google knows this.

There’s a wonderful report that you should take time to read called “Patterns in Unstructured Data” provided by the National Institute for Technology in Liberal Education or NITLE which gives a fantastic explanation of how LSI works .

If you do a search on “Tiger Woods” or “Apple”, Google is smart enough to detect a few things about these terms such as the fact that Tiger Woods is a golfer, and that Apple is a company that has iPhones.

This would mean that if you created a web page about iPhones another likely word you might include on your page would be “Apple”.

Here’s a screen shot from Google when searching on the term “Apple”. Notice in all of the initial 10 listings are occurrences of the computer company not the actual fruit. And at the bottom of the page are still even more related words to “Apple”.

The same holds true for any words and phrases. And Google makes it easy for us to spot what it believes are related words to virtually any term you decide to create a web page on.

While at Google.com place the tilde symbol ~ directly in front of each word you intend on using within your content. Google will return to you what it believes to be semantically related words for each term you placed after that symbol.

Let’s take the example of the word “soap”. Soap is a pretty generic term, it could mean the soap you wash with, a “Soap Opera” or even the protocol “SOAP” which stands for Simple Object Access Protocol. How Google determines the relevance of the word you’re writing about is by also taking a look at the semantically related words you use within that content.

So if you were writing about the kind of soap you wash with, you might use terms like:

spa
body
candle
scented
bar
massage

On the other hand if you were writing about a soap opera you might use terms like:

Guiding Light
The Young and the Restless
The Bold and the Beautiful

The fact is, Google knows that if it finds the word “soap” in the same document as “body”, “candle” or “spa” you are most likely referring to bath soap and it will rank you accordingly.

This is why semantically related terms or LSI is so important. It is using words and phrases throughout your content that all relate to the overall word or phrase of the content itself.

This is also why plurals are not helpful. Plurals are not semantically related terms. They are simply, plurals. As an example, if you used the words “soap” and “soaps” on a web page, Google would have no idea what to do with that content because there are no additional semantically related terms on the page.

The bottom line is, when writing your content you do want to use semantically related terms within that content so that the search engines understand what that web page is about. This will help the search engines understand and rank your web pages accordingly.