A threshold, or limit, refers to a specific point or level at which something begins or changes. It can be used in various contexts, such as in science, where it might indicate the minimum amount of a substance needed to trigger a reaction, or in psychology, where it defines the level of stimulus required for a person to notice a change. In everyday life, thresholds can also apply to physical spaces, like the entrance of a room, marking the transition from one area to another. Understanding thresholds helps in setting boundaries and recognizing when conditions are met for a particular outcome, whether in experiments, behavioral studies, or architecture.