A standard curve is commonly used in scientific research to measure the concentration of a certain substance. Synonyms for a standard curve include calibration curve, reference curve, control curve, comparison curve, and assay curve. These terms all refer to a graph that plots known concentrations of a substance against a measurable response, typically absorbance or fluorescence. The resulting curve can then be used to determine the concentration of an unknown sample by comparing its response to the curve. Standard curves are essential for accurate quantitative analysis and are used in a wide range of fields, from biochemistry to environmental science.