The concept of saturation can be described using various naming systems, formulas, and analytical tests. For instance, IUPAC nomenclature is a system of naming conventions used to describe the type and location of unsaturation within organic compounds. The "degree of unsaturation" is a formula used to summarize and diagram the amount of hydrogen that a compound can bind. Unsaturation can be determined by NMR, mass spectrometry, and IR spectroscopy, or by determining a compound's bromine number or iodine number.