diffusion
n. uncountable C1 Advanced US //dɪfˈjuʒən// UK //dɪfjˈuːʒən// dif·fu·sion
n. the process of something spreading out and mixing with its surroundings. You see this when a drop of ink slowly spreads through a glass of water.
n. the gradual mixing of particles from an area of high concentration to an area of low concentration until equilibrium is reached.
The diffusion of heat warms the whole room.
The diffusion of the scent filled the kitchen within minutes.
In biology, the diffusion of oxygen across cell membranes allows tissues to receive the energy they need to survive.
Borrowed from Latin diffūsiō, from diffundō; can be decomposed as diffuse + -ion.