A dATa type composed of multiple elements. An aggregATe can be homogeneous (all elements have the same type) e.g. an array, a list in a functional language, a string of characters, a file or it can be heterogeneous (elements can have different types) e.g. a structure. In most languages aggregATes can contain elements which are themselves aggregATes. e.g. a list of lists. See also union. (1996-03-23)