Thermal diffusion, also known as thermodiffusion or the Soret effect, is not a term that has a specific medical definition. It is a physical phenomenon that occurs in a mixture of two or more substances when there is a temperature gradient present. As a result, the components of the mixture tend to separate based on their differences in molecular weight and heat conductivity.

However, thermal diffusion can have indirect applications in certain medical contexts, such as in the development of medical devices or in understanding the behavior of biological systems at the molecular level. For instance, it may be relevant in the design of microfluidic devices used for lab-on-a-chip applications, where precise control over the movement and separation of molecules is essential.

In summary, while thermal diffusion itself does not have a medical definition, its principles and applications can be significant in certain medical and biomedical research contexts.

Diffusion, in the context of medicine and physiology, refers to the process by which molecules move from an area of high concentration to an area of low concentration until they are evenly distributed throughout a space or solution. This passive transport mechanism does not require energy and relies solely on the random motion of particles. Diffusion is a vital process in many biological systems, including the exchange of gases in the lungs, the movement of nutrients and waste products across cell membranes, and the spread of drugs and other substances throughout tissues.