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)