An "indicator" is a measurable value that provides information about a specific condition or trend. It helps to assess progress, performance, or changes in various fields, such as economics, health, or environmental science. For example, the Gross Domestic Product (GDP) is an economic indicator that reflects a country's economic performance. Indicators can be quantitative, like statistics, or qualitative, like surveys. They are often used in research and decision-making to guide actions and policies. In public health, for instance, the infant mortality rate serves as an important indicator of healthcare quality and overall societal well-being.