The synonym feature allows you relate two or more words together to form a synonym set. A synonym set will help capture alternative terminology that a user might use in their search queries. As a globally available website, you will have visitors that use very different language -- it is valuable to be ahead of their search patterns.
For example, if you had an eCommerce website which sold cars, you might have a user conduct searches for: car, vehicle, jalopy, automobile, or one of the many other ways of phrasing a four wheeled transportation device.
Site Search Analytics will reveal the words that users are using to search. If you notice terms being used that are different than the ones that you expect, create a synonym set. You can also preemptively configure a synonym set. Synonyms are added at the Engine level and are bound however you set them -- they have no bearing on whether or not the words are actual synonyms.
You can create synonyms within the dashboard...
To create a synonym set, login to Site Search and click into your Engine.
Within the Sidebar or the Engine Overview, click on Synonyms
To add a synonym, click on the Create a Synonym Set button or the link within the supporting text.
You are now able to combine various words to make your set.
Add fields until you are satisfied, then click Save Synonym Set
Once you click save, your synonym will be active -- you can test it out within Search Preview.
If you want to edit or delete a synonym set, click the edit button next to the set, then click delete or alter the set however you would like.
That is it! You have successfully configured synonyms.