• In science, magnitude refers to the numerical size of something: see orders of magnitude.
• In mathematics, the magnitude of an object is a non-negative real number, which in simple terms is its length.
• In astronomy, magnitude refers to the logarithmic measure of the brightness of an object, measured in a specific wavelength or passband, usually in optical or near-infrared wavelengths: see apparent magnitude and absolute magnitude.
• In Seismology , the magnitude is a logarithmic measure of the energy released during an earthquake. See Richter scale and moment magnitude scale.