1. in classical psychoanalytic theory, the view that the personality comprises three divisions or functions: (a) the id, which represents instinctual drives; (b) the ego, which controls id drives and mediates between them and external reality; and (c) the superego, which comprises moral precepts and ideals. Sigmund Freud proposed this model in 1923 to replace his earlier topographic model, in which the mind was divided into three regions: the unconscious, preconscious, and conscious. Also called structural approach; structural hypothesis; structural theory. See also dynamic model; economic model.

2. in statistics, any theoretical representation of the relationships among a dependent variable and multiple independent variables, whether continuous or discrete. Techniques to derive such models include latent class analysis, path analysis, and structural equation modeling.