Multiplicity (1)
Multiplicity is a [meta-] property of relations that counts the number of N-tuples in which a specific instance of the corresponding entity type can appear.
Each N-ary relation has a defined set of N possible multiplicity [meta-]attributes.
Each multiplicity attribute denotes the size or number of instances in the projection of the relation (as a set of points) on a single component of the N-tuple.
This is the number of instances of one entity type/role that can be related to one tuple of instance values for the N-1 other types/roles.