Scott Bowler

Latent Semantic Indexing (LSI) for Dummies

In the world of SEO there are a number of terms which don’t make any sense when you first read them. Latent Semantic Indexing, or LSI, is one of them. You may have heard terms such as “the semantic web” or “semantic searches” and to get to the root of what LSI is it’s important to understand first what semantics actually is.

Semantics is the study of the meaning of words and sentances. Take the phrase “he was taller” - this could have many meanings depending on the context. For example, I could be talking about a male Giraffe being taller than the rest of animals in the herd (or anything else that relates to tallness and the male sex). If I was to extend this phrase a bit further and say “he was taller than me” then we would understand the context to be talking about humans.

Google’s mission statement is “to organize the world’s information and make it universally accessible and useful” and this is where semantics comes into play. They have written complex algorithms to understand what a page is about by analysing the words and phrases on a web site and how their meanings (or semantics) are related. This process is known as Latent Semantic Indexing.

“But” I hear you all cry “what does this have to do with optimising my website for the search engines?”. The answer is: a lot. People have fallen into the habit of stuffing their target keywords into content using sentances and phrases which are difficult or clunky for people to read. I’m sure you’ve all read (or even written) sentances such as “Our extremely talented SEO team can help with your SEO needs to ensure that your site is SEO friendly and will beat your competition’s SEO campaign”. It doesn’t make for good reading, does it?

Fortunately, there is a solution, and thanks to the new LSI algorithms we can write content which flows much more freely and will actually boost our rankings for searches which are related to our target keywords.

The key to optimising your website for Latent Semantic Indexing is to think about words which semantically support your target keyword. If we were optimising for the term “SEO”, then semantic phrases or keywords could include:

• online marketing
• PR
• boost
• improve
• rankings

Now our poorly written phrase from before can be turned into “Our extremely talented online marketing team can help with your PR needs to ensure that your site is SEO friendly and will beat your competition’s rankings in the search engines”. We have now given our sentance significantly more context by using words and phrases which are semantically similar to our target keyword.

LSI doesn’t just apply to single sentances, paragraphs or articles. The search engine algorithms can look at an entire website to analyse its semantics so it is important to make sure that the content is semantically relevant and consistant throughout the website.

In the coming months and years you will see a shift in how the search engines deliver their results. For example, if you were to search for a phrase such as “online shopping” the search engines may semantically analyse this term and return a result for a website which contains the phrase “buy on the web”.

Semantics, it means a lot.

And heres a great little video by pixwrh1 for a quick explanation:

The Magic LSI Latent Semantic Indexing for Keyword Ranking

Technorati Tags: SEO, Latent Semantic Indexing, LSI, semantic web, semantic searches, semantics, context, Google, algorithms, optimising, search engines, target keywords, LSI algorithms, online marketing, PR

Tags: algorithms, animals, giraffe, google, habit, herd, latent semantic indexing, lsi, male sex, mission statement, phrase, search engines, semantic web, semantics, seo, target keywords