Cybernetics is the interdisciplinary study of the structure of regulatory systems.
Cybernetics is closely related to information theory, control theory and systems theory, at least in its first-order form. (Second-order cybernetics has crucial methodological and epistemological implications that are fundamental to the field as a whole.)
Both in its origins and in its evolution in the second half of the 20th century, cybernetics is equally applicable to physical and social (that is, language-based) systems.