Probability measure
![In some cases, statistical physics uses probability measures, but not all measures it uses are probability measures.[1][2]](/Images/godic/202502/04/Maxwell-Distr2912.png")
![](/Images/godic/202502/04/Nuvola_apps_atlantik2912.png")
![A probability measure mapping the probability space for 3 events to the unit interval.](/Images/godic/202502/04/Probespazio2912.png")
In mathematics, a probability measure is a real-valued function defined on a set of events in a probability space that satisfies measure properties such as countable additivity. The difference between a probability measure and the more general notion of measure (which includes concepts like area or volume) is that a probability measure must assign value 1 to the entire probability space.