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Sigma (/ ˈ s ɪ ɡ m ə / SIG-mə; [1] uppercase Σ, lowercase σ, lowercase in word-final position ς; Ancient Greek: σίγμα) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 200. In general mathematics, uppercase Σ is used as an operator for summation.
the standardized regression coefficient for predictor or independent variables in linear regression (unstandardized regression coefficients are represented with the lower-case Latin b, but are often called "betas" as well) the ratio of collector current to base current in a bipolar junction transistor (BJT) in electronics (current gain)
The x must be lowercase in XML documents. The nnnn or hhhh may be any number of digits and may include leading zeros. The hhhh may mix uppercase and lowercase, though uppercase is the usual style. In contrast, a character entity reference refers to a character by the name of an entity which has the desired character as its replacement text.
The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC. [2] [3] It was derived from the earlier Phoenician alphabet, [4] and is the earliest known alphabetic script to have developed distinct letters for consonants as well as vowels. [5]
Historically, upper-case letters were used for representing points in geometry, and lower-case letters were used for variables and constants. Letters are used for representing many other sorts of mathematical objects. As the number of these sorts has remarkably increased in modern mathematics, the Greek alphabet and some Hebrew letters are also ...
sigma: summation operator area charge density: coulomb per square meter (C/m 2) electrical conductivity: siemens per meter (S/m) normal stress: pascal (Pa) scattering cross section: barn (10^-28 m^2) surface tension: newton per meter (N/m) tau: torque: newton meter (N⋅m) shear stress: pascal time constant: second (s)
Uppercase and lowercase Greek letter sigma, from the times.ttf font included with standard XOrg X Windows installations. Intended to replace Image:Sigma.png . Category:Greek letters
These characters allow any polynomial, chemical and certain other equations to be represented in plain text without using any form of markup like HTML or TeX. The World Wide Web Consortium and the Unicode Consortium have made recommendations on the choice between using markup and using superscript and subscript characters: