A spectrum is a range of different entities that are ordered by some common characteristic, often depicted as a line or curve with the different entities represented along this line. In the context of research, a spectrum is often used to describe a range of values, categories, or variables that can vary in nature or intensity. Researchers use spectra to analyze and understand relationships between different entities and to categorize or classify them based on similarities or differences. Spectra can be used in a wide variety of research areas, including physics, chemistry, biology, and social sciences, to name just a few.