Diffusion and advection both are transport phenomenon (movement of substances). 

The main differentiating factor between the two are:

• -Diffusion occurs without any bulk flow.
• -Advection occurs with bulk flow.

Diffusion and advection together is convection.

thanks!

Regards,

Rajesh.

Diffusion and advection both are transport phenomenon (movement of substances). 

The main differentiating factor between the two are:

• -Diffusion occurs without any bulk flow.
• -Advection occurs with bulk flow.

Diffusion and advection together is convection.

thanks!

Regards,

Rajesh.

They are two completely different things. Advection is the general motion of a fluid or gas, such as a river streaming from a high point to a low point. It is a macroscopic effect that involves the entire fluid.

Diffusion is the motion of a fluid inside another substance (another fluid, usually) and occurs on micro level (individual molecules).

both are transport phenomena

In diffusion transportation occurs by molecule to molecule ...it will happen even if there is no bulk motion on substance...i.e. conduction

In advection transport occurs because of the motion of particles,let's say heat diffuse when there is bulk motion..

hope you get the answer..