Answer:
High concentration to low concentration with or without a partially permeable membrane
Step-by-step explanation:
Diffusion is the movement of particles from a region of high concentration (where there is alot of the particle) to a region of low concentration (where there is less of the particle) until it is evenly distributed.
The definition didn't state whether or not a partially permeable membrane was required.
It doesn't have to pass through a membrane. for e.g. spraying perfume at one side of the room and it is smelt on the other side. Meaning it diffused through the room. There was no membrane present.
It can also pass through a membrane for e.g diffusion of oxygen gas into cells (cells have membranes therefore the oxygen diffused through the membrane.)