Lewin formally defines a Gestalt as:
a system whose parts are dynamically connected in such a way that a change of one part results in a change of all other parts.
p. 218, as cited in: Granville Stanley Hall, Edward Bradford Titchener, Karl M. Dallenbach (1937) The American journal of psychology. Vol. 50, p. 374. - Principles of topological psychology, 1936