The term "impossible" refers to something that cannot be done or achieved. It often describes tasks or events that defy the laws of nature, logic, or current understanding. For example, creating a perpetual motion machine is considered impossible because it violates the laws of thermodynamics. In everyday life, people may use "impossible" to express doubt about achieving a goal, such as running a marathon without training. However, what seems impossible today may become possible in the future as technology and knowledge advance, illustrating that the definition of "impossible" can change over time.