There is considerable variation in the dynamical literature in how the term "complexity" is used. While there have been several attempts to describe from an educational perspective what complexity encompasses, the term is frequently used without an explicit definition. To forge a shared understanding of what complexity means, the purpose of this article is to define the term for the field in a way that acknowledges the variety of use that is encountered in the education. Four perspectives on complexity are offered: 1) Information theory, 2) Cybernetics and general systems theory, 3) The use of complexity to describe scenarios of transformation and 4) Complexity as a metatheory. The implications of each of these four conceptualizations for educational research and practice are discussed.