Multiplicity   multiplicity is a property of an association end that specifies the number of instances of the classifier connected at the target end (near end) that can be associated with a single instance of the classifier at the source end (far end). It is specified in the form of a string stipulating a possible infinite number governed by a lower and upper bound.

Explanation

Multiplicity is one of the most important properties of an association end and expresses significant semantics about the relationship between the classifiers that participate in the association. It is important to remember that an association that involves just two classifiers is a special case, called a binary association; the more general association is the n-ary association. The multiplicity property specifies the number of instances of the classifier at the association end under discussion that are permitted to be linked with just one instance of the classifier at the other end or the source end. Some confusion exists because the multiplicity at the far (source) end may be some number other than one. To read the multiplicity correctly one must "artificially" set the source multiplicity to one. This is simply a device used to read the multiplicity.