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A multiplicity fraction is the fraction of a set of star systems (taking it to mean either single or multiple stars) that have multiple stars. For example, the Milky Way would have a multiplicity fraction, as would the set of "all G-type stars". If a set of twenty individual stars is comprised of four binary stars plus twelve individual stars, then the set's multiplicity fraction is 25% because four of sixteen systems have multiple stars. The same set of stars could be characterized by other fractions besides this defined multiplicity fraction: for example, 40% (eight of twenty) of the set's individual stars are within multiple star systems.