Previously, we had to search for the exact words that would be found on a web page. Now we can search for the concept. When we do a Google search, Google will find matches of the keyword, will find stem variations of the word, and now will also find synonyms of the keyword (words that are related to the keyword).
This was recently posted in The Official Google Blog: "We have made several notable advances including ... an advanced synonyms system. Synonyms are the foundation of our query understanding work. This is one of the hardest problems we are solving at Google. Though sometimes obvious to humans, it is an unsolved problem in automatic language processing.
As a user, I don't want to think too much about what words I should use in my queries. Often I don't even know what the right words are. This is where our synonyms system comes into action.
Our synonyms system can do sophisticated query modifications, e.g., it knows that the word 'Dr' in the query [Dr Zhivago] stands for Doctor whereas in [Rodeo Dr] it means Drive. A user looking for [back bumper repair] gets results about rear bumper repair. For [Ramstein ab], we automatically look for Ramstein Air Base; for the query [b&b ab] we search for Bed and Breakfasts in Alberta, Canada. We have developed this level of query understanding for almost one hundred different languages."
So, with almost no fanfare, Google has started the automatic use of synonyms in its searching. This is a step beyond stemming which Google has been doing for the last 5 years. With stemming, if you search for obit, you also get results for obits and obituary - variations of the same word. Now that Google is also searching for synonyms, obit might also return web pages that use the words death notice.
Previously, search for NJ and you only got pages that contained NJ. Google didn't consider New Jersey a match. Now, with synonym searching, it does.
Up until now, Google did not do synonym searching unless you specifically used the Google tilde synonym operator ~ .
This is a big algorithm change. Yet the change is so subtle that most people probably won't even notice it except to note that their Google results seem a bit better. Now people don't have to guess the exact words a webmaster uses on his web page to find the web page via Google.
However, we may not always want synonym searches such as when we are searching for surnames that are also common words. With this algorithmic change, we need to adjust the way we do some genealogy searches.
When I search for one of my surnames Powers, I not only receive the stemming words for Powers such as Power and Powered, now I also might receive synonyms such as Strengths. If I only want exact name Powers results with no stems and no synonyms, now I need to put a plus before the surname for an exact search. +Powers
If the surname you are searching for is Street, and find you are getting unwanted synonyms such as St. and Road, search for +Street to search for the exact word with no stemming and no synonyms. A plus sign before the surname with no space in between tells Google to search for that exact word.
Now that Google has added synonym matching for its search results, Google Personalized Search becomes even more important as it helps Google understand our queries better based on our past searching. And understanding how the Google Search Algorithm works is important because it can help us form better search queries.