The tags "context-free" and "context-free-languages" are clear synonyms. Could somebody with the appropriate reputation (2.5k+) please do the deed?
As a side issue/rant, it's annoying that options aren't even visible if you don't have enough reputation. It took me a long time to find out that the reason I couldn't directly suggest these as synonyms was because I don't have enough reputation, not because I was looking in the wrong place. The interface would be much more intuitive if the link to create new synonyms was visible but produced an error message. And why on earth does such a simple operation require so much reputation?