The pricess due to which particles move from a region of high concentration to low concentration , is known as diffusion .

The spontaneous movement of a substance from their region of higher concentration to the region where its concentration is low is known as diffusion.
Intermixing of two or more particles on their own is diffusion
The spontaneous movement of molecules of a substance from a region of higher concentration to lower conceration is called diffusion
The movement of substances from region of high concentration to low concentration is called diffusion