S

The dollar sign, also known as the peso sign, is a currency symbol consisting of a capital ⟨S⟩ crossed with one or two vertical strokes ($ or depending on typeface), used to indicate the unit of various currencies around the world, including most currencies denominated "dollar" or "peso". The explicitly double-barred sign is called cifrão in the Portuguese language.

The sign is also used in several compound currency symbols, such as the Brazilian real (R$) and the United States dollar (US$): in local use, the nationality prefix is usually omitted. In countries that have other currency symbols, the US dollar is often assumed and the "US" prefix omitted.

In statistics, the standard deviation is a measure of the amount of variation of the values of a variable about its mean. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the values are spread out over a wider range. The standard deviation is commonly used in the determination of what constitutes an outlier and what does not. Standard deviation may be abbreviated SD or std dev, and is most commonly represented in mathematical texts and equations by the lowercase Greek letter σ (sigma), for the population standard deviation, or the Latin letter s, for the sample standard deviation.

The standard deviation of a random variable, sample, statistical population, data set, or probability distribution is the square root of its variance. (For a finite population, variance is the average of the squared deviations from the mean.) A useful property of the standard deviation is that, unlike the variance, it is expressed in the same unit as the data. Standard deviation can also be used to calculate standard error for a finite sample, and to determine statistical significance.

The long s, ⟨ſ⟩, also known as the medial s or initial s, is an archaic form of the lowercase letter ⟨s⟩, found mostly in works from the late 8th to early 19th centuries. It replaced one or both of the letter s in a double-s sequence (e.g., "ſinfulneſs" for "sinfulness" and "poſſeſs" or "poſseſs" for "possess", but never "poſſeſſ"). The modern ⟨s⟩ letterform is known as the "short", "terminal", or "round" s. In typography, the long s is known as a type of swash letter, commonly referred to as a "swash s". The long s is the basis of the first half of the grapheme of the German alphabet ligature letter ⟨ß⟩, (eszett or scharfes s, 'sharp s'). As with other letters, the long s may have a variant appearance depending on typeface: ſ, ſ, ſ, ſ.

Sigma (/ˈsɪɡmə/ SIG-mə; uppercase Σ, lowercase σ, lowercase in word-final position ς; Ancient Greek: σίγμα) is the eighteenth letter of the Greek alphabet. When used at the end of a letter-case word (one that does not use all caps), the final form (ς) is used. In Ὀδυσσεύς (Odysseus), for example, the two lowercase sigmas (σ) in the center of the name are distinct from the word-final sigma (ς) at the end.

In the system of Greek numerals, sigma has a value of 200. In general mathematics, uppercase Σ is used as an operator for summation. The Latin letter S derives from sigma while the Cyrillic letter Es derives from a lunate form of this letter.

In statistics, the standard deviation is a measure of the amount of variation of the values of a variable about its mean. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the values are spread out over a wider range. Standard deviation may be abbreviated SD or std dev, and is most commonly represented in mathematical texts and equations by the lowercase Greek letter σ (sigma), for the population standard deviation, or the Latin letter s, for the sample standard deviation.

The standard deviation of a random variable, sample, statistical population, data set, or probability distribution is the square root of its variance. (For a finite population, variance is the average of the squared deviations from the mean.) A useful property of the standard deviation is that, unlike the variance, it is expressed in the same unit as the data. Standard deviation can also be used to calculate standard error for a finite sample, and to determine statistical significance.

Shin (also spelled Šin (šīn) or Sheen) is the twenty-first and penultimate letter of the Semitic abjads, including Phoenician šīn 𐤔, Hebrew šīn ש‎, Aramaic šīn 𐡔, Syriac šīn ܫ, and Arabic sīn س‎.

The Phoenician letter gave rise to the Greek Sigma (Σ) (which in turn gave rise to the Latin S, the German ẞ and the Cyrillic С), and the letter Sha in the Glagolitic and Cyrillic scripts (, Ш). The South Arabian and Ethiopian letter Śawt is also cognate. The letter šīn is the only letter of the Arabic alphabet with three dots with a letter corresponding to a letter in the Northwest Semitic abjad or the Phoenician alphabet.

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  The Venus de Milo statue has an S-curve form.
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  Diagram S-curve form of Doryphoros by Polykleitos

In the visual arts, an S-curve is an S-shaped curve that serves a wide variety of compositional purposes. The term is usually applied to the standing human figure bending first one way and then back the other. It may also be applied more generally, for example in landscape painting and photography.

The digraph sh in the Latin alphabet is written as a combination of S and H.