A 'stereotypical movement' denotes a movement reproduced in a standardised form. The term is used in two fields, in movement science and in medical assessments of pathology. The former recognises the occurrence of regular patterns of movement across individuals expressed at regular points in development, such as the pre-reach in early infancy. The latter specifies a pathological form of repetitive movement by one individual symptomatic of, for example, autism. This entry explores the interindividual use of the term in movement science and touches on ongoing work to better classify and quantify stereotypical movements for better psychophysiological understanding of action development, and possible sensitive measures of them.