When I search for the Keyword: "Mediation" I get highlights in my search results for Mediation and Mediator.

Does this mean that Google considers them to be synonyms?

If so, then what are the implications for those highlights?

By the way, Google says they are two different categories for Keywords on my Webmaster tools. Mediator and Mediators are one category, while Mediate, Mediating, Mediations, Mediation are a second category.