a specialization of Participation that expresses an "is part of / is composed of" Fact. The terms in the fact describe the component types of the whole. See Chapter 4

a way that one class can refer to another class without having possession of it + a weak form of 'has-a' / APO link + if the whole object is an aggregation then deleting it does not effect the existence of the aggregated part. This relationship is shown by an open diamond at one end of a link. The other end may have an arrow head indicating the link can be navigated in one direction only.

An aggregation relationship is a 'whole-part' relationship, e.g. a page is a part of a book.

several things grouped together or considered as a whole

a bunch of parts

a special form of association that models a whole-part relationship between an aggregate (the whole) and its parts

a special form of association that shows a relationship between a whole (the aggregate ) and its parts

a "whole-part" association within which one element is "part" of the larger "whole" of the other element

a tightly coupled form of association, between a whole and its parts, in which the whole is composed of the parts

(UML) An association in which one class represents an assembly of components from one or more other class types. Components may also exist without being part of the assembly. aggregate.php

A group or mass of distinct things or individuals. Gathered into, or considered as, a whole; total.

Summation of part s. Typically used in reference to estimating. [D02367] RMW An association that model s a whole- part relationship between an aggregate (the whole) and its part [D04800] RUP

A special form of association that specifies a whole-part relationship between the aggregate (whole) and a component part. Contrast: composition.