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In addition, the SI Brochure provides style conventions for among other aspects of displaying quantities units: the quantity symbols, formatting of numbers and the decimal marker, expressing measurement uncertainty, multiplication and division of quantity symbols, and the use of pure numbers and various angles.
The names and symbols of SI base units are written in lowercase, except the symbols of those named after a person, which are written with an initial capital letter. For example, the metre has the symbol m, but the kelvin has symbol K, because it is named after Lord Kelvin and the ampere with symbol A is named after André-Marie Ampère.
Unit symbol Dimension symbol Quantity name Definition In SI base units In other SI units SI: Physics: Basic: second [n 1] s: T: time:
Symbol Description SI base unit Dimension Comments Amount of substance: n: The quantity proportional to the number of particles in a sample, with the Avogadro constant as the proportionality constant: mole (mol) N: extensive, scalar Length: l: The one-dimensional extent of an object metre (m) L: extensive: Time: t: The duration of an event ...
The second is the international standard unit (SI unit) for science. Celestial sphere-based: as in sidereal time, where the apparent movement of the stars and constellations across the sky is used to calculate the length of a year. These units do not have a consistent relationship with each other and require intercalation. For example, the year ...
Symbol Name Meaning SI unit of measure alpha: alpha particle: angular acceleration: radian per second squared (rad/s 2) fine-structure constant: unitless beta: velocity in terms of the speed of light c: unitless beta particle: gamma: Lorentz factor: unitless photon: gamma ray: shear strain: radian
Before and in addition to the SI, other metric systems include: the MKS system of units and the MKSA systems, which are the direct forerunners of the SI; the centimetre–gram–second (CGS) system and its subtypes, the CGS electrostatic (cgs-esu) system, the CGS electromagnetic (cgs-emu) system, and their still-popular blend, the Gaussian ...
The current international standard for the metric system is the International System of Units (Système international d'unités or SI). It is a system in which all units can be expressed in terms of seven units. The units that serve as the SI base units are the metre, kilogram, second, ampere, kelvin, mole, and candela.