What is the meaning of diffusion coefficient?

[phyky]

diffusion coefficient meaning is the coefficient of particles diffuse when different in concentration. How about diffusion coefficient of a particle? the trajectory where a particle diffuse?

 

[Kholdstare]

Sorry I don't get your question clearly. There is no diffusion coefficient of a single particle, as diffusion coefficient is a statistical quantity and applicable to a collection of particle. Just like average marks of a single person's marks is meaningless.