A threshold, or limit, refers to a specific point or level at which something begins or changes. It can apply to various contexts, such as science, psychology, and everyday life. For example, in psychology, a pain threshold is the minimum intensity of a stimulus that causes a person to feel pain. In science, thresholds are often used to describe the limits of certain processes, like the temperature at which a substance changes from solid to liquid. Understanding thresholds helps in setting boundaries and making decisions in various fields, including healthcare and environmental science.