No, "decoherence" and "wave function collapse" are not two words describing the same natural phenomenon. They refer to distinct concepts in quantum mechanics.
Decoherence: Decoherence is a process in quantum mechanics that explains how a quantum system, which initially exists in a superposition of multiple states, becomes entangled or correlated with its surrounding environment. As a result of interactions with the environment, the system's coherence is gradually lost, leading to a loss of quantum interference effects and the appearance of classical behavior. Decoherence does not involve any abrupt or instantaneous collapse of the wave function.
Wave Function Collapse: Wave function collapse, also known as wave function reduction or the collapse of the wave packet, is a concept in quantum mechanics that occurs when an observer measures or interacts with a quantum system. According to the Copenhagen interpretation of quantum mechanics, the act of measurement causes the system's wave function to "collapse" into a definite state corresponding to the measurement result. This collapse is usually seen as a sudden, discontinuous change from a superposition of possibilities to a single, determinate outcome.
While both decoherence and wave function collapse are related to the behavior of quantum systems, they describe different aspects of quantum mechanics. Decoherence refers to the loss of quantum coherence due to interactions with the environment, which leads to the appearance of classical behavior. On the other hand, wave function collapse refers to the sudden reduction of the system's wave function upon measurement or interaction with an observer.