I’ve been using this word a lot in my first-semester Criminal Law and Torts classes, and finally one student had the nerve to ask me what it meant. I thought everyone knew, but just as a fish is said to not perceive the water in which it swims, so I didn’t recognize that the word is legalese. I just thought it was plain English, but, like conclusory, it’s not. So for the benefit of other entering law students (and perhaps even others), here’s the scoop.

In many legal contexts, dispositive means (to quote one of the definitions from Merriam-Webster’s Dictionary of Law):

providing a final resolution (as of an issue) : having control over an outcome < dispositive of the question>.

One way of remembering this is by looking at the stem, which turns out to be “dispose of,” as in “dispose of the question” (in the sense of “to deal with conclusively; settle”). Here’s an example from a Supreme Court case:

Of course, the scope of the material-support statute may not be clear in every application. But the dispositive point here is that the statutory terms are clear in their application to plaintiffs’ proposed conduct, which means that plaintiffs’ vagueness challenge must fail.

The dispositive point is the one that means that disposes of the plaintiffs’ challenge — that, in this case, “means that plaintiffs’ … challenge must fail” (though in other contexts “dispositive” might mean dispositive in a way that means plaintiffs’ challenge succeeds).

There are also sometimes more-or-less figurative meanings of dispositive, as well as meanings related to dispositions of property (i.e., who gets what under a will). But this is the meaning that professors, judges, and lawyers often use to refer to matters that themselves dispose of a question, as opposed to just being one of many factors that are relevant to the question’s resolution.