| ′ | |||||||
|---|---|---|---|---|---|---|---|
Prime | |||||||
| |||||||
Theprime symbol′,double prime symbol″,triple prime symbol‴, andquadruple prime symbol⁗ are used to designate units and for other purposes inmathematics,science,linguistics andmusic.
Although the characters differ little in appearance from those of theapostrophe and single and doublequotation marks, the uses of the prime symbol are quite different.[1] While an apostrophe is now often used in place of the prime, and a double quote in place of the double prime (due to the lack of prime symbols on everyday writing keyboards), such substitutions are not considered appropriate in formal materials or intypesetting.
The prime symbol′ is commonly used to representfeet (ft), and the double prime″ is used to representinches (in).[2] The triple prime‴, as used inwatchmaking, represents aligne (1⁄12 of a "French" inch, orpouce, about 2.26 millimetres or 0.089 inches).[3]
Primes are also used forangles. The prime symbol′ is used forarcminutes (1⁄60 of a degree), and the double prime″ forarcseconds (1⁄60 of an arcminute).[4] As an angular measurement,3° 5′ 30″ means 3degrees, 5 arcminutes and 30 arcseconds. In historical astronomical works, the triple prime was used to denote "thirds" (1⁄60 of an arcsecond)[5][6] and a quadruple prime⁗ "fourths" (1⁄60 of a third of arc),[a] but modern usage has replaced this withdecimal fractions of an arcsecond.
Primes are sometimes used to indicate minutes, and double primes to indicate seconds of time, as in theJohn Cage composition4′33″ (spoken as "four thirty-three"), a composition that lasts exactly 4 minutes 33 seconds. This notation only applies to duration, and is seldom used for durations longer than 60 minutes.[8][better source needed]
In mathematics, the prime is generally used to generate more variable names for similar things without resorting to subscripts, withx′ generally meaning something related to (or derived from)x. For example, if a point is represented by theCartesian coordinates(x,y), then that point rotated, translated or reflected might be represented as(x′,y′).
Usually, the meaning ofx′ is defined when it is first used, but sometimes, its meaning is assumed to be understood:
The prime is said to "decorate" the letter to which it applies. The same convention is adopted infunctional programming, particularly inHaskell.
Ingeometry,geography andastronomy, prime and double prime are used as abbreviations forminute and second of arc (and thuslatitude,longitude,elevation andright ascension).
Inphysics, the prime is used to denote variables after an event. For example,vA′ would indicate the velocity of object A after an event. It is also commonly used in relativity: the event at(x, y, z, t) inframeS, has coordinates(x′, y′, z′, t′) in frameS′.
Inchemistry, it is used to distinguish between different functional groups connected to an atom in a molecule, such asR andR′, representing differentalkyl groups in anorganic compound. Thecarbonyl carbon in proteins is denoted asC′, which distinguishes it from the otherbackbone carbon, thealpha carbon, which is denoted asCα. Inphysical chemistry, it is used to distinguish between the lower state and the upper state of aquantum number during a transition. For example,J ′ denotes the upper state of the quantum numberJ whileJ ″ denotes the lower state of the quantum numberJ.[10]
Inmolecular biology, the prime is used to denote the positions of carbon on a ring ofdeoxyribose orribose. The prime distinguishes places on these two chemicals, rather than places on other parts ofDNA orRNA, likephosphate groups ornucleic acids. Thus, when indicating the direction of movement of anenzyme along a string of DNA, biologists will say that it moves from the5′ end to the3′ end, because these carbons are on the ends of the DNA molecule. The chemistry of this reaction demands that the3′ OH be extended by DNA synthesis. Prime can also be used to indicate which position a molecule has attached to, such as5′-monophosphate.
The prime can be used in thetransliteration of somelanguages, such asSlavic languages, to denotepalatalization. Prime and double prime are used to transliterate Cyrillicyeri (the soft sign, ь) andyer (the hard sign, ъ).[11] However, inISO 9, the corresponding modifier letters are used instead.
Originally,X-bar theory used a bar over syntactic units to indicate bar-levels insyntactic structure, generally rendered as anoverbar. While easy to write, the bar notation proved difficult to typeset, leading to the adoption of the prime symbol to indicate a bar. (Despite the lack of bar, the unit would still be read as "X bar", as opposed to "X prime".) With contemporary development of typesetting software such asLaTeX, typesetting bars is considerably simpler; nevertheless, both prime and bar markups are accepted usages.
Some X-bar notations use a double prime (standing in for a double-bar) to indicate a phrasal level, indicated in most notations by "XP".
The prime symbol is used in combination with lower case letters in theHelmholtz pitch notation system to distinguish notes in differentoctaves frommiddle C upwards. Thusc represents the⟨C⟩ below middle C,c′ represents middle C,c″ represents the⟨C⟩ in the octave above middle C, andc‴ the⟨C⟩ in the octave two octaves above middle C. A combination of upper case letters and sub-prime symbols is used to represent notes in lower octaves. ThusC represents the⟨C⟩ below the bass stave, whileC ͵ represents the⟨C⟩ in the octave below that.
In some musical scores, the double prime″ is used to indicate a length of time in seconds. It is used over afermata𝄐 denoting a long note or rest.[b]
Unicode and HTML representations of the prime and related symbols are as follows.
The "modifier letter prime" and "modifier letter double prime" characters are intended for linguistic purposes, such as the indication ofstress or the transliteration of certainCyrillic characters.[citation needed]
In a context when the character set used does not include the prime or double prime character (e.g., in an online discussion context where only ASCII orISO 8859-1 [ISO Latin 1] is expected), they are often respectively approximated by ASCII apostrophe (U+0027) or quotation mark (U+0022).
LaTeX provides an oversized prime symbol,\prime (), which, when used in super- or sub-scripts, renders appropriately; e.g.,f_\prime^\prime appears as. An apostrophe,', is a shortcut for a superscript prime; e.g.,f' appears as.
.Une ligne équivaut à 2,2558 mm, que l'on arrondit généralement à 2,26 mm.[Aligne equates to 2.2558 mm, which is typically rounded to 2.26mm]
| Page | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Paragraph | |||||||||||
| Character |
| ||||||||||
| Typeface classifications |
| ||||||||||
| Punctuation (List) | |||||||||||
| Typesetting | |||||||||||
| Typographic units | |||||||||||
| Digital typography | |||||||||||
| Typography in other writing systems | |||||||||||
| Related articles | |||||||||||
| Related template | |||||||||||
