Magnitude refers to a measurable value, typically one that relates to a scale from very small to very large. It could be size, length, brightness, volume, or whatever. But it would not be used to refer to direction or to color or something that cannot be called "small" or "large". Generally it is used to differentiate between an event with multiple values, such as the magnitude of an explosion (Was it big? But not where did it occur or what direction did it go in?) Generally think of it as "size", although sometimes that isn't quite appropriate. (i.e. The magnitude of a star refers to its apparent size.)
The term magnitude is usually addressed to size, extent as well as dimensions. In mathematics the magnitude of a particular article is its volume.
It is a property which can be bigger or lesser than articles of the same type, according to technical terms, an arrangement of the class of articles to which it belongs. The negative magnitude was not thought to be so important, and even till today magnitude is mainly used in contexts in which zero is moreover the smallest size or less than all probable sizes.
In realistic math a magnitude can never be negative. While evaluating magnitudes, it is generally advisable to use a logarithmic scale. In simple terms it is not always important to add or subtract magnitudes.
The word Magnitude is basically derived from Latin language. It was used in Latin as Magnitudo meaning Greatness, size etc.
This word is used to refer to greatness of rank or position, size or extent. It could also be used for greatness in significance or influence. It helps in ordering of a class of objects.
1. The degree of brightness of a star or other celestial body, measured on a logarithmic scale in which lower numbers mean greater brightness, such that a decrease of one unit represents an increase in brightness by a factor of 2.512. An object that is 5 units less than another object on the magnitude scale is 100 times more luminous. Because of refinements in measurement after the zero point was assigned, very bright objects have negative magnitudes. The brightness of a celestial body as seen from Earth is called its apparent magnitude. (When unspecified, an object's magnitude is normally assumed to be its apparent magnitude.) The dimmest stars visible to the unaided eye have apparent magnitude 6, while the brightest star in the night sky, Sirius, has apparent magnitude -1.4. The full Moon and the Sun have apparent magnitudes of -12.7 and -26.8 respectively. The brightness of a celestial body computed as if viewed from a distance of 10 parsecs (32.6 light-years) is called its absolute magnitude. Absolute magnitude measures the intrinsic brightness of a celestial object rather than how bright it appears on Earth, using the same logarithmic scale as for apparent magnitude. Sirius has an absolute magnitude of 1.5, considerably dimmer than Rigel which, though its apparent magnitude is 0.12, has an absolute magnitude of -8.1. Stars that appear dim in the night sky but have bright absolute magnitudes are much farther from Earth than stars that shine brightly at night but have relatively dim absolute magnitudes. The Sun, a star of only medium brightness, has an absolute magnitude of 4.8. The degree of total radiation emitted by a celestial body, including all infrared and ultraviolet radiation in addition to visible light, is called its bolometric magnitude. Bolometric magnitude is generally measured by applying a standard correction to an object's absolute magnitude. 2. A measure of the total amount of energy released by an earthquake, as indicated on the Richter scale. See more at Richter scale.
