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Multiplicity Fraction

(fraction of star systems that are multiple-star systems)

A Multiplicity Fraction is the fraction of a set of star systems that have multiple stars. For example, the Milky Way would have a multiplicity fraction, as would th set of all G-Type Stars.

If a set of twenty stars is comprised of four Binary Stars plus twelve individual stars, then the set's multiplicity fraction would be 25% since four of sixteen systems have multiple stars. Yet eight of twenty or 40% of the set's stars are in multiple star systems.

The term Planet Multiplicity can be applied to Extra Solar Planet systems in an analogous manner. Among other things, this has been used in statistical studies to verify planet discoveries, i.e., Verification by Multiplicity.