In a post on the Official Google Blog, Google opens up the curtains a bit on how it handles synonyms in search queries and results. It’s a fairly detailed peek inside one aspect of Google’s search algorithms — an aspect that Google says affects a lot of searches:
“…our measurements show that synonyms affect 70 percent of user searches across the more than 100 languages Google supports. We took a set of these queries and analyzed how precise the synonyms were, and were happy with the results: For every 50 queries where synonyms significantly improved the search results, we had only one truly bad synonym.”
Google shares an example of a bad synonym: substituting “pc” as a synonym for “precision” in a search query like [dell system speaker driver precision 360].
Google also says it’s changing how synonyms are displayed in search results: Rather than only bolding direct variants of words (like “photos” for “pictures”), Google has “extended this to words that our algorithms very confidently think mean the same thing, even if they are spelled nothing like the original term.”
On his personal blog, Matt Cutts follows up the official post with some words of advice for webmasters:
“Think about the different words that searchers might use when looking for your content. Don’t just use technical terms–think about real-world terms and slang that users will type. For example, if you’re talking about a “usb drive,” some people might call it a flash drive or a thumb drive.”
The official post also mentions that users can turn off synonyms by putting a plug sign (+) before a word in your query, or by putting the query in quotation marks.
Not mentioned in either post is that you can use the tilde symbol (~) to force Google to show additional synonyms (and related words) for your query. For example, a search for [~murder statistics] leads Google to bold words like “crime,” “crime statistics,” “suicide statistics,” “criminal,” and more.