If something is conclusive, it shows that a thing is definitely true — or definitely not true. Conclusive evidence. A conclusive test. A conclusive victory. The argument can stop because this settles it. It is a strong, rather formal word; in science and in court it means “this is enough; we are not still guessing.” Though actually, people sometimes call a result conclusive when it is only strong, and another study later knocks it down. Still, the word itself claims a high bar: not “this suggests,” but “this shows.” It is not the same as concluding, which only means “coming last.”