A theoreticals (or conceptual) definition is an abstract concept that defines a term in an academic discipline. Without a falsifiable operational definition, conceptual definitions assume both knowledge and acceptance of the theories that it depends on.[1] A hypothetical construct may serve as a theoretical definition, as can a stipulative definition.

A theoretical definition is a proposed way of thinking about potentially related events [1][2] Indeed, theoretical definitions contain built-in theories; they cannot be simply reduced to describing a set of observations. The definition may contain implicit inductions and deductive consequences that are part of the theory.[3] A theoretical definition of a term can change, over time, based on the methods in the field that created it.