Movement of factors (eg, molecules, ions) from high concentration to low concentration. Used by cells/organsisms to move factors at minimal cost.
Regional difference in concentration of a factor. (Party room analogy...150 ppl will move into other room faster then 10ppl due to the nature of humans)
How readily a medium permits diffusion
Some factors diffuse through, some don't (eg, a cell membrane)
Formation of a macromolecule, also called dehydration synthesis.