Is "negotiation room" a correct expression? I'd like to use it in a sentence such as "there is still some room for negotiation on the terms and conditions." The idea is to show that we are still open to negotiate on some specific topics. Thank you in advance.
A search for the phrase "some room for negotiation" in Google Books returns about 50 unique matches, while a search for the phrase "some negotiating room" returns about 45 unique matches; a search for the phrase "some room to negotiate" yields about 30 unique matches, as does a search for the phrase "some room for negotiating"; and a search for the phrase "some negotiation room" returns 20 unique matches.
So of the five options cited above, the most common ways of expressing this particular idea in books included in the Google Books database are "some room for negotiation" and "some negotiating room," and the least common way (by a considerable margin) is "some negotiation room."
Although (as commenters above suggest) either "negotiation room" or "negotiating room," when used by itself, may refer to the physical room where negotiations take place, I didn't see any instances in the search matches where either of the longer phrases "some negotiation room" and "some negotiating room" referred to such a physical space. It follows that you may use any of the five expressions listed in the first paragraph of my answer to fill in the blank in the clause "there is still ______________ on the terms and conditions," without fear of being misunderstood.