In the study of psychology, idiographic describes the study of the individual, whereas nomothetic is more the study of a cohort of individuals.

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Nomothetic and idiographic are terms coined by Kantian philosopher Wilhelm Windelband to describe two distinct approaches to knowledge, each one corresponding to a different intellectual tendency, and each one corresponding to a different branch of academe.

Nomothetic is based on what Kant described as a tendency to generalize, and is expressed in the natural sciences. It describes the effort to derive laws that explain objective phenomena.

Idiographic is based on what Kant described as a tendency to specify, and is expressed in the humanities. It describes the effort to understand the meaning of contingent, accidental, and often subjective phenomena.