An ion or group of ions having a positive charge and characteristically moving toward the negative electrode in electrolysis.
An atom, or group of atoms with a positive charge. Cation exchange is the process whereby a cation in solution is absorbed by a solid, replacing a different cation. Thus, in soil science, if a potassium salt is dissolved in water and applied to a soil, potassium cations are absorbed by soil particles, and sodium and calcium cations are released.