Coherent structures cannot superimpose, i.e. they cannot overlap and each coherent structure has its own independent domain and boundary. Since eddies coexist as spatial superpositions, a coherent structure is not an eddy. For example, eddies dissipate energy by obtaining energy from the mean flow at large scales, and eventually dissipating it at the smallest scales. There is no such analogous exchange of energy between coherent structures, and any interaction such as tearing between coherent structures simply results in a new structure. However, two coherent structures can interact and influence each other. The mass of a structure change with time, with the typical case being that structures increase in volume via the diffusion of vorticity.