Capillary action occurs when the fluid surface in a small tube rises or lowers in relation to the surrounding normal fluid.
The raising of fluid in a tube is known as capillary rise, whereas the decrease of the fluid level is known as capillary fall.
Capillary depression occurs when the cohesive energy between the particles of the liquid exceeds the adhesive force between both the particles of the fluid and the particles of the container.
Mercury in a capillary tube shows a capillary depression.
Capillary action occurs when the adhesive force to the walls is higher than the cohesive forces between the liquid molecules.
