flow

Flow is a term with several meanings across different fields. In psychology, flow describes a mental state of complete absorption in an activity, often accompanied by enjoyment and a sense of mastery. In physics and engineering, flow refers to the motion of a fluid substance, such as a liquid or gas, driven by pressure differences and resisted by viscosity.

In psychology, the flow state is characterized by intense concentration, a merging of action and awareness, a loss of self-consciousness, a sense of control, and a distortion of time. It often occurs when challenges are well matched to a person’s skills and immediate feedback is available. The concept was popularized by Mihaly Csikszentmihalyi and has been studied in education, sport, and work design.

In physics, fluid flow is described by a velocity field and is categorized as laminar or turbulent based on flow smoothness. Governing principles include the continuity equation and, for many applications, the Navier–Stokes equations. Quantities such as the Reynolds number help predict regimes of flow. Flow analysis underpins hydraulics, aerodynamics, weather, and many engineering disciplines.

Flow is also used in computing and business to describe sequences of operations or transfers of data, often referred to as data flow or control flow, or as workflow and process flow in organizational processes. In physiology and health, blood flow refers to the circulation of blood through vessels. In environmental contexts, river flow describes the discharge and velocity of water in a stream or river.