The functional (not statistical) relationship for the chemical measurement process, relating the expected value of the observed (gross) signal or response variable Ey to the analyte amount x. The corresponding graphical display for a single analyte is referred to as the calibration curve. When extended to additional variables or analytes which occur in multicomponent analysis, the 'curve' becomes a calibration surface or hypersurface.
PAC, 1995, 67, 1699. 'Nomenclature in evaluation of analytical methods including detection and quantification capabilities (IUPAC Recommendations 1995)' on page 1703 (https://doi.org/10.1351/pac199567101699)