The process by which a feature spreads from one place to another 

They are the channels by which molecules enter in facilitated diffusion.

Diffusion of AIDS is an example of contagious diffusion, where the disease spreads through direct or indirect contact between individuals.

Diffusion can take place in any substance, cause diffusion means the mixture of gases . In a perfume shop diffusion takes place

Is Diffusion the movement of molecules from a greater to a lesser concentration.