Chaos refers to the unpredictable, random-like motion of deterministic dynamic systems, because it is sensitive to initial values. Also known as chaos. The English word Chaos comes from Greek. Its original meaning is the scene before the beginning of the universe, and its basic meaning mainly refers to the chaotic state. As a scientific term, the word chaos refers to a form of motion. The certainty of dynamic system is a mathematical concept, which means that the state of the system at any moment is determined by the initial state. Although the motion state at any time in the future can be calculated according to the initial state data and motion law, the prediction result is bound to be wrong or even unpredictable because the initial data cannot be completely accurate. The predictability of motion is a physical concept. Even if a motion is deterministic, it can still be unpredictable, which is not contradictory.

The success of Newtonian mechanics, especially the success of predicting Neptune, has caused misunderstanding to some extent, equating certainty with predictability, and holding that deterministic motion must be predictable. The research after 1970s shows that although the system is deterministic, the chaotic motion which is extremely sensitive to the initial value of the motion state, seemingly random and unpredictable generally exists in a large number of nonlinear systems. Chaos refers to a seemingly irregular and complex form of motion that exists in the real world. * * * Homologous is an orderly movement form that originally followed simple physical laws. Under certain conditions, it suddenly deviates from the expected regularity and becomes a disorderly form. Chaos can appear in many deterministic dynamic systems. Chaos is similar to stochastic process in statistical characteristics, and it is considered to be inherent randomness in deterministic systems.