What is Latent Semantic Indexing?
Latent Semantic Indexing refers to the way in which search engines determine the context of a website’s content in order to successfully match it to a user’s search. For example, a website could use the word 'java' but this has multiple and very different meanings. Therefore, to ensure that the word is not matched to an unrelated search, a search engine would use latent semantic indexing to evaluate the rest of the content. For example, a search engine would have to decide whether the word 'java' referred to coffee, a country or the computer programming language. This is achieved by looking at the co-occurrence of signal words in the document or document set. So, using the term 'java' with other references to beverages would sway the search engine towards coffee being the correct meaning within its context. Using this technique to rank websites means that search engines are giving more weight to the central themes or intent of websites as opposed to the density of specific keywords. It is therefore crucial that website owners stick to Google's recommendations and make their content as explicit as possible while backing up their keyphrases with related terms.
Optimising your website content
There are various things you can do to make sure that your website content is clear and more easily matched with related searches. You can still use keywords and keyphrases but Google will penalise pages it deems as ‘over-optimised’ so be careful to only use them where they sound natural. It is also important to make sure that you use related words to describe terms that could be misinterpreted. For example, if you have a product listed that is described as ‘tangerine’, make sure you relate the word ‘colour’ to it in the description so as to distance your site from the definition of tangerine as a fruit. It is also a good idea to use keywords and keyphrases in your ALT text for an image which depicts what you are referring to. An explicit reference describing the image will help to make the context and purpose of your site crystal clear.