In physics, topological order is a kind of order in zero-temperature phase of matter (also known as quantum matter). Macroscopically, topological order is defined/described by robust ground state degeneracy and quantized non-Abelian geometric phases of degenerate ground states (just like superfluid order is defined/described by vanishing viscosity and quantized vorticity). Microscopically, topological order corresponds to patterns of long-range quantum entanglement (just like superfluid order corresponds to boson condensation). States with different topological orders (or different patterns of long range entanglements) cannot change into each other without a phase transition.