Diffusio

Diffusio is a term used to describe the process by which substances, energy, or signals spread from regions of higher concentration to regions of lower concentration. The word derives from Latin diffusio, meaning “a spreading out,” and it is applied across disciplines to denote passive transport that does not require external energy input.

In physics and chemistry, diffusion is modeled by Fick’s laws and the diffusion equation. The diffuse flux is driven by concentration gradients, with a species-specific diffusion coefficient determining the rate. Molecules undergo random Brownian motion, leading to gradual mixing and the equilibration of concentrations over time.

In biology and medicine, diffusion explains how nutrients, gases, and pharmaceutical compounds move through membranes and tissues. It underpins many processes of cellular exchange and drug delivery, where the spreading of a compound from an administration site to target cells can influence efficacy and safety. Diffusible molecules may form gradients that influence cellular behavior in certain contexts, reflecting the practical importance of diffusion in living systems.

Beyond the physical sciences, diffusio is used metaphorically to describe the spread of ideas, innovations, or information through populations or networks. Diffusion models borrowed from physics are commonly employed in social science, epidemiology, and communication studies to understand adoption patterns, reach, and speed of dissemination.

See also: Diffusion, Fick’s laws, Brownian motion, diffusion coefficient, diffusion of innovations.