Relativity analytics allows you to run searches for documents with terms that are conceptually similar to those you enter. Relativity will group together terms that appear in the workspace's data set (rather than relying on a universal conceptually dictionary that groups similar terms in a static set). A user running a search with the Analytics index has the option to click on the Expand link to get a list of the concept set for an entered string.
So if you're searching for 'baseball', and Relativity analytics will prompt you to include keywords like bat, field, diamond, glove, and so forth.
When viewing an individual document, a user can also simply select a keyword from the document image, and right click . . . Analytics . . . Keyword Expansion, and results will be shown in a pop-up window.