Solr provides the option to configure synonyms for use during both indexing and querying of textual data. A synonym is a word or phrase that means exactly or nearly the same thing as another word or phrase in the same language. For example, shut is a synonym of close. Synonyms, if not accounted for, can cause a dilution of search result relevancy when searching for a keywords that have lots of variations in your index.
Consider for example the words, "ipod", "i-pod", and "i pod". It's pretty easy to imagine a scenario in which the content of our site could contain all three variations of the word. When someone searches though they are likely just going to search for one, but expect results for all three. In order to not break those expectations we need to make sure we account for this scenario. Another example from the the Drupal world would be the terms "CMI" and "configuration management". Chances are if you search for one you would be happy to see results for the other.
In this tutorial we'll look at using the synonyms.txt file that is part of our Solr configuration in order to account for synonyms in our data. Of course the exact words you use will depend on the content of your site, but we can at least cover how they work and how to configure them.
By the end of this tutorial you should be able to configure Solr to be aware of synonyms in your data in order to improve the quality of your search results.