Google search keeps getting smarter and smarter. Search relevancy scores have changed recently. Insiders attribute this to latent semantic indexing, which Google had already been using, but recently increased its weighting to make this algorithm all the more important. So what is it?

Latent semantic indexing allows a search engine to determine what a page is about outside of specifically matching search query text. A page about Apple computers will likely naturally have terms such as iMac or iPod on it…By placing additional weight on related words in content LSI has a net effect of lowering the value of pages which only match the specific term and do not back it up with related terms. Source

To give another specific example:

In an AP news wire database, a search for Saddam Hussein returns articles on the Gulf War, UN sanctions, the oil embargo, and documents on Iraq that do not contain the Iraqi president’s name at all. Source

Question: How do you know if your content is laced with enough related keywords to rank well in this new world of latent semantic indexing?

Answer: Search Google for search results with related terms using a ~. For example, Google Search: ~computer will return pages with terms matching or related to computer and will highlight some of the related words in the search results. In this example you can see hardware and Laptop show up on the first page of search results, showing how deeply important these related keywords are to improving the relevancy of your content. If Google is showing related keywords in the first couple of pages which your content lacks, rework your content to include these terms.

For further reading on the latent semantic indexing: