Utente:Grasso Luigi/sandbox/Sopralineato

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Descrizione	Esempi	Unicode	CSS/HTML
	generico
	combinato
	composto
Sopralineato (codifica)	Xx	N.D.	text-decoration: overline;
Overline (carattere)	‾	U+203E	‾, ‾
	X̅x̅ (combinato)	U+0305	X̅
Sopralineato doppio (codifica)	Xx	N.D.	text-decoration: overline;  text-decoration-style: double;
Sopralineato doppio (carattere)	X̿x̿ (combinato)	U+033F	X̿
Macron (carattere)	¯	U+00AF	¯, ¯
	X̄x̄ (combinato)	U+0304	X̄
	X̄x̄ (carattere composto )	variabile

Una sopralinea, un sovrassegno, o una sovrastringa, è un simbolo tipografico che consiste di una linea orizzontale sopra un testo. Nella notazione matematica antica, una sopralinea veniva detta un vincolo, una notazione per raggruppare i simboli che nella notazione moderna è espressa tramite parentesi, sebbene persista per i simboli sotto il segno di radicale. L'uso originale in lingua greca antica indicava composizioni di lettere greche nel sistema di numerazione greco.^[1] In Latino, indica i numeri romani moltiplicati per mille e forma le abbreviazioni medievali (abbreviazione scribale). La formattazione di una o più parole con una linea continua sopra i carattteri viene a volte detta sovrastampa, sebbene la sovrastampa in genere si riferisca alla stampa di un carattere sopra un carattere già stampato.

Una sopralinea, ovvero una singola riga sopra una porzione di testo, non deve essere confusa con il segno di macron, un segno diacritico posto sopra (a volte sotto) caratteri singoli. Il macron è più stretto del rettangolo che contiene un carattere.^[2]

Utilizzo

Medicina

  Lo stesso argomento in dettaglio: Abbreviazione scribale, Acronimi in medicina e Macron (segno diacritico).

Nella maggior parte delle forme di abbreviazione scribale in latino, una sopralinea o macron indica lettere omesse simili all'uso dell'apostrofo nelle contrazioni inglesi. I caratteri con una macron o una sopralinea continuano a essere utilizzati in abbreviazioni mediche in varie lingue europee, in particolare nelle prescrizioni. Vediamo alcuni esempi

• a, a̅, o ā per ante (prima)
• c, c̅, or c̄ for Template:Linktext ("with")
• p, p̅, or p̄ for Template:Linktext ("after")^[3]
• q, q̅, or q̄ for Template:Linktext and its inflections ("every", "each")
• s, s̅, or s̄ for Template:Linktext ("without")
• x, x̅, or x̄ for Template:Linktext and its inflections ("except")

Note, however, that abbreviations involving the letter h take their macron halfway up the ascending line rather than at the normal height for Unicode overlines and macrons: ħ. This is separately encoded in Unicode with the symbols using bar diacritics and appears shorter than other overlines in many fonts.

Matematica e scienza

Separatore decimale

  Lo stesso argomento in dettaglio: Decimal separator.

In the Middle Ages, from the original Indian decimal writing, before printing, an overline over the units digit was used to separate the integral part of a number from its fractional part, as in 9995 (meaning 99.95 in decimal point format). A similar notation remains in common use as an underbar to superscript digits, especially for monetary values without a decimal separator, as in 99^{Template:Underline}.^{[senza fonte]}

Vinculum

In mathematics, an overline can be used as a vinculum.

The vinculum can indicate a line segment:^[4]$${\displaystyle {\overline {\rm {AB}}}}$$ The vinculum can indicate a repeating decimal value: $${\displaystyle {1 \over 7}=0.{\overline {142857}}=0.142857142857142857142857...}$$  When it is not possible to format the number so that the overline is over the digit(s) that repeat, one overline character is placed to the left of the digit(s) that repeat: $${\displaystyle 3.{\overline {\phantom {I}}}3=3.{\overline {3}}=3.3333333333333333333333333...}$$  $${\displaystyle 3.12{\overline {\phantom {I}}}34=3.12{\overline {34}}=3.123434343434343434343434...}$$  Historically, the vinculum was used to group together symbols so that they could be treated as a unit. Today, parentheses are more commonly used for this purpose.

Statistics

The overline is used to indicate a sample mean:^[5]

• ${\displaystyle {\overline {x}}}$  is the average value of ${\displaystyle x_{i}}$ 

Survival functions or complementary cumulative distribution functions are often denoted by placing an overline over the symbol for the cumulative: ${\displaystyle {\overline {F}}(x)=1-F(x)}$ .

Negation

In set theory and some electrical engineering contexts, negation operators (also known as complement) can be written as an overline above the term or expression to be negated.^[6] For example:

Common set theory notation:

${\displaystyle {\begin{aligned}{\overline {A\cup B}}&\equiv {\overline {A}}\cap {\overline {B}}\\{\overline {A\cap B}}&\equiv {\overline {A}}\cup {\overline {B}}\end{aligned}}}$ 

Electrical engineering notation:

${\displaystyle {\begin{aligned}{\overline {A\cdot B}}&\equiv {\overline {A}}+{\overline {B}}\\{\overline {A+B}}&\equiv {\overline {A}}\cdot {\overline {B}}\end{aligned}}}$ 

in which the times (cross) means multiplication, the dot means logical AND, and the plus sign means logical OR.

Both illustrate De Morgan's laws and its mnemonic, "break the line, change the sign".

Negative

In common logarithms, a bar over the characteristic indicates that it is negative—whilst the mantissa remains positive. This notation avoids the need for separate tables to convert positive and negative logarithms back to their original numbers.

${\displaystyle \log _{10}0.012\approx -2+0.07918={\bar {2}}.07918}$ 

Complex numbers

The overline notation can indicate a complex conjugate and analogous operations.^[7]

• if ${\displaystyle x=a+ib}$ , then ${\displaystyle {\overline {x}}=a-ib.}$ 

Vector

In physics, an overline sometimes indicates a vector, although boldface and arrows are also commonly used:

• ${\displaystyle {\overline {x}}=|x|{\hat {x}}}$ 

Congruence classes

Congruence modulo Template:Math is an equivalence relation, and the equivalence class of the integer Template:Math, denoted by Template:Math, is the set Template:Math}. This set, consisting of all the integers congruent to Template:Math modulo Template:Math, is called the congruence class, residue class, or simply residue of the integer Template:Math modulo Template:Math. When the modulus Template:Math is known from the context, that residue may also be denoted Template:Math or Template:Math.

Topological closure

In topology, the closure of a subset S of a topological space is often denoted Template:Math or ${\displaystyle \operatorname {cl} S}$ .

Improper rotation

In crystallography, an overline indicates an improper rotation or a negative number:

• ${\displaystyle {\overline {3}}}$  is the Hermann–Mauguin notation for a threefold rotoinversion, used in crystallography.
• ${\displaystyle [{\overline {1}}1{\overline {2}}]}$  is the direction with Miller indices ${\displaystyle h=-1}$ , ${\displaystyle k=1}$ , ${\displaystyle l=-2}$ .

Maximal conductance

In computational neuroscience, an overline is used to indicate the "maximal" conductances in Hodgkin-Huxley models. This goes back to at least the landmark paper published by Nobel prize winners Alan Lloyd Hodgkin and Andrew Fielding Huxley around 1952.^[8]

${\displaystyle I_{\mathrm {Na} }(t)={\bar {g}}_{\mathrm {Na} }m(V_{m})^{3}h(V_{m})(V_{m}-E_{\mathrm {Na} })}$ 

Antiparticles

Overlines are used in subatomic particle physics to denote antiparticles for some particles (with the alternate being distinguishing based on electric charge). For example, the proton is denoted as Template:Subatomic particle, and its corresponding antiparticle is denoted as Template:Subatomic particle.

Engineering

An active low signal is designated by an overline, e.g. RESET, representing logical negation.

Graphics Design

Overlining is also used in graphics design for decoration of text to help convey a message.^[9]

Morse (CW)

Some Morse code prosigns can be expressed as two or three characters run together, and an overline is often used to signify this. The most famous is the distress signal, SOS.

Writing

An overline-like symbol is traditionally used in Syriac text to mark abbreviations and numbers. It has dots at each end and the center. In German it is occasionally used to indicate a pair of letters which cannot both be fitted into the available space (also see the use of macron in German writing).^[10][11]

When Morse code is written out as text, overlines are used to distinguish prosigns and other concatenated character groups from strings of individual characters.

In Arabic writing and printing, overlines are traditionally used instead of underlines for typographic emphasis,^[12] although underlines are used more and more due to the rise of the internet.

 

Overlines used in a version of the Bible in Persian (1920)

Linguistics

X-bar theory makes use of overbar notation to indicate differing levels of syntactic structure. Certain structures are represented by adding an overbar to the unit, as in X. Due to difficulty in typesetting the overbar, the prime symbol is often used instead, as in XTemplate:Prime. Contemporary typesetting software, such as LaTeX, has made typesetting overbars considerably simpler; both prime and overbar markers are accepted usages. Some variants of X-bar notation use a double-bar (or double-prime) to represent phrasal-level units.

X-bar theory derives its name from the overbar. One of the core proposals of the theory was the creation of an intermediate syntactic node between phrasal (XP) and unit (X) levels; rather than introduce a different label, the intermediate unit was marked with a bar.

Implementations

HTML with CSS

In HTML using CSS, overline is implemented via the text-decoration property; for example, <span style="text-decoration: overline">text</span> results in: text.

The text decoration property supports also other typographical features with horizontal lines: underline (a line Template:Underline the text) and strikethrough (a line Template:Strikethrough the text).

Unicode

Unicode includes two graphic characters, U+00AF ¯ MACRON and U+203E ‾ OVERLINE. They are compatibility equivalent to the U+0020   SPACE with non-spacing diacritics U+0304 ◌̄ COMBINING MACRON and U+0305 ◌̅ COMBINING OVERLINE respectively; the latter allows an overline to be placed over any character. There is also U+033F ◌̿ COMBINING DOUBLE OVERLINE. As with any combining character, it appears in the same character box as the character that logically precedes it: for example, x̅, compared to x‾. A series of overlined characters, for example 1̅2̅3̅, may result either in a broken or an unbroken line, depending on the font.

In Unicode, character U+FE26 Template:Smallcaps2 is conjoining (bridging) two characters: ◌︦◌.

In East Asian (CJK) computing, U+FFE3 ￣ FULLWIDTH MACRON is available. Despite the name, Unicode maps this character to both U+203E and U+00AF.^[13]

Unicode maps the overline-like character from ISO/IEC 8859-1 and code page 850 to the U+00AF ¯ MACRON symbol mentioned above. In a reversal of its official name (and compatibility decomposition), it is much wider than an actual macron diacritic over most letters, and actually wider than U+203E ‾ OVERLINE in most fonts. In ChromeOS and Linux, the symbol can be added using the keystrokes Ctrl+⇧ Maiusc+U to activate Unicode input, then type "00AF" as the code for the character. On a Mac, with the ABC Extended keyboard, use Option+a. In Microsoft Windows, U+00AF can be entered with the keystrokes Alt+01+7+5 (where numbers are entered from the numeric keypad).

The Unicode character U+070F SYRIAC ABBREVIATION MARK is used to mark Syriac abbreviations and numbers. However, several computer environments do not render this line correctly or at all.

The Unicode character U+0B55 ୕ ORIYA SIGN OVERLINE is used as a length mark in Odia script.

Word processors

Collabora Online, an office suite for the web has direct menu support for several styles of Overline in the "Format" menu, with options available under "Format > Character" enabling the default solid Overline to be replaced with double overline, dots, dashes, waves, double waves, and the color of the Overline can be set.

Collabora Office and LibreOffice have direct menu support for several styles of Overline in the "Format" menu. The user-interface option is available in their word processors on Linux, macOS and Windows, and also in Android (in tablet format), ChromeOS and iPadOS with Collabora Office. Options for Overline are available under the menu: "Format > Character", enabling the default solid Overline to be replaced with double overline, dots, dashes, waves, double waves, and the color of the Overline can be set.

Microsoft Word does not have a menu option to edit Overlining in Microsoft Word for any operating system, or in Word for the web. Overlining can be added using fields codes, EQ \O(). The field code {EQ \O(x,¯)} produces x and the field code {EQ \O(xyz,¯¯¯)} produces xyz; However this does not work in Word on Android, ChromeOS, iPadOS, or Word for the web. In Word 2010 it is necessary to insert an MS Equation object.

Overstriking of longer sections of text, such as in 123, can also be produced in many text processors as text markup as a special form of understriking.

Spreadsheet, Presentation and Graphics office suite applications

Collabora Online, Collabora Office and LibreOffice have direct menu support for several styles of Overline in the "Format" menu within applications of their office suites, including spreadsheets, presentations and graphics applications. The user-interface option is available in the web based suite, and the locally installable applications for Linux, macOS and Windows, and with Collabora Office in Android (in tablet format), ChromeOS and iPadOS. Options for Overline are available under the menu: "Format > Character", enabling the default solid Overline to be replaced with double overline, dots, dashes, waves, double waves, and the color of the Overline can be set.

TeX

In LaTeX, a text <text> can be overlined with $\overline{\mbox{<text>}}$. The inner \mbox{} is necessary to override the math-mode (here invoked by the dollar signs) which the \overline{} demands.

Note

1. ^ (EN) Smith, T. P., How Big is Big and How Small is Small: The Sizes of Everything and Why, OUP, 2014, ISBN 978-0199681198.
2. ^ (EN) Wells, J.C., Orthographic diacritics and multilingual computing, su phon.ucl.ac.uk, UCL. URL consultato il 23-03-14.
3. ^ Adriano Cappelli, Manuali Hoepli Lexicon Abbreviature Dizionario Di Abbreviature Latine ed Italiane, Milan, Editore Ulrico Hoepli Milano, 1961, p. 256.
4. ^ Line Segment Definition - Math Open Reference, su mathopenref.com.
5. ^ Sample Means, su stat.yale.edu.
6. ^ Set Operations | Union | Intersection | Complement | Difference | Mutually Exclusive | Partitions | De Morgan's Law | Distributive Law | Cartesian Product, su probabilitycourse.com.
7. ^ (EN) Eric W. Weisstein, Complex Conjugate, su mathworld.wolfram.com.
8. ^ A quantitative description of membrane current and its application to conduction and excitation in nerve, in The Journal of Physiology, vol. 117, n. 4, 1952, pp. 500–544, DOI:10.1113/jphysiol.1952.sp004764.
9. ^ Overline vs: Underline: Unraveling the Differences, su fastercapital.com, Faster Capital, 18 June 2024. URL consultato l'8 September 2024.
10. ^ Gräfinnen, su flickr.com, 23 novembre 2011.
11. ^ Lieder zur Weihnachtszeit (1940), su fontsinuse.com, 26 dicembre 2015.
    
    «It used to be common to mark omitted double letters with an overbar, especially for "mm" and "nn". These abbreviations come in handy when lyrics have to match the musical notes, see 'da kom[m]t er her'.»
12. ^ Emphasis (typography), su graficnotes.blogspot.com.
13. ^ The Unicode Consortium, The Unicode Standard 6.1, Unicode Consortium, 2012.

Voci correlate

• Ā, un grafema con A latina con una macron
• Titlo, un sopralineato usato per indicare numeri o abbreviazioni in cirillico
• Trattino basso

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