Unicode character property: Difference between revisions

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{{Short description|Unicode code- point property names and their uses}}

{{Use British English|date=January 2025}}

The [[Unicode Standard]] assigns various properties to each Unicode character and [[code point]].<ref name="Chapter4">{{cite web|url=https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-4/|date=September 2024|title=The Unicode Standard Version 16 |publisher=The Unicode Consortium |access-date=2024-09-13}}</ref><ref name="UAX44" />

The properties can be used to handle characters (code points) in processes, like in line-breaking, script direction right-to-left or applying controls. Some "character properties" are also defined for code points that have no character assigned and code points that are labeledlabelled like "&lt;not a character>&gt;". The character properties are described in Standard Annex #44.<ref name="UAX44">{{cite web |url=https://www.unicode.org/reports/tr44/ |title=Unicode Standard Annex #44: Unicode Character Database |website=Unicode |date=2024-08-27}}</ref>

Properties have levels of forcefulness: normative, informative, contributory, or provisional. For simplicity of specification, a character property can be assigned by specifying a continuous range of code points that have the same property.<ref>{{cite web|url=https://www.unicode.org/reports/tr44/#Code_Point_Ranges|title=Unicode Standard Annex #44: Unicode Character Database, 4.2.3 Code Point Ranges|website=Unicode |date=2024-08-27}}</ref>

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[code];[name];[gc];[cc];[bc];[decomposition];[nv-dec];[nv-dig];[nv-num];[bm];[alias];;[upper case];[lower case];[title case]

*'<code>alias'</code> = corrected name. Obsolete. Now tracked with a separate database, but remains for Unicode 1.0 names etc.

*'<code>bc'</code> = bidi (bidirectional) category [L, R etc]

*'<code>bm'</code> = bidi mirrored [N or Y]

*'<code>cc'</code> = combining class [position of diacritic]

*<code>decomposition</code> type or <mapping> = letter + diacritic, ligature X Y, superscript X, font X, initial X, medial X, final X, isolated X, vertical X, etc.

*'<code>gc'</code> = general category [letter, symbol, digit, punctuation, case behaviorbehaviour, etc.]

*'<code>nv'</code> = numeric type and value [of a digit]. If numeric type is 'decimal', all 3 slots are filled. If 'digit', the first will be null. (This has been discontinued.) If 'numeric', then the first two will be null and only the last will be used.

The property between '<code>alias'</code> and '<code>upper case'</code> is obsolete and is now null for all Unicode characters.

==Code==

The first property is the hexadecimal [[code point]].

=={{anchor|Name}}Name and alias==

A Unicode character is assigned a unique '''Name''' (na).<ref name="Chapter4"/> The name is composed of uppercase letters A–Z, digits 0–9, [[hyphen-minus (-)]] and space[[Space ( punctuation)|space]]. Some sequences are excluded: names beginning with a space or hyphen, names ending with a space or hyphen, repeated spaces or hyphens, and space after hyphen are not allowed. The name is guaranteed to be unique within Unicode, and can be used to identify a code point and its character. Ideographic characters, of which there are tens of thousands, are named in the pattern "{{Smallcaps|{{lc:CJK UNIFIED IDEOGRAPH}}}}-''hhhh''". For example, {{unichar|4E00|CJK UNIFIED IDEOGRAPH-4E00}}. Formatting characters arealso namedhave toonames: {{unichar|00A0|NO-BREAK SPACE}}.

The following classesUnicode of code pointcategories do not have a Name (na="")value assigned: Controls (General Category: Cc), Private use (Co), Surrogate (Cs), Non-characters (Cn) and Reserved (Cn). They may be referenced, informally, by a generic or specific meta-name, called "Code Point Labels": {{not a typo|<control>, <control-0088>, <reserved>, <noncharacter-''hhhh''>, <private-use-''hhhh''>, or <surrogate>}}. Since these labels contain "<" and ">-brackets", they can never appear asin a Name, which prevents confusion.

==={{anchor|Version 1.0 names}}Unicode 1.0 names===

The following classes of code point do not have a Name (na=""): Controls (General Category: Cc), Private use (Co), Surrogate (Cs), Non-characters (Cn) and Reserved (Cn). They may be referenced, informally, by a generic or specific meta-name, called "Code Point Labels": {{not a typo|<control>, <control-0088>, <reserved>, <noncharacter-''hhhh''>, <private-use-''hhhh''>, or <surrogate>}}. Since these labels contain <>-brackets, they can never appear as a Name, which prevents confusion.

In version 2.0 of Unicode, many names were changed. From then on the rule "a name will never change" came into effect, including the strict (normative) use of alias names. Disused versionUnicode 1.0- names were moved to the property Alias, to provide some backward compatibility.

For example, {{Unichar|264}} has the Unicode 1.0 name "LATIN SMALL LETTER BABY GAMMA".

===Version 1.0 names===

In version 2.0 of Unicode, many names were changed. From then on the rule "a name will never change" came into effect, including the strict (normative) use of alias names. Disused version 1.0-names were moved to the property Alias, to provide some backward compatibility.

===Character name alias===

{{main|Unicode alias names and abbreviations}}

Starting from Unicode version 2.0, the published name for a code point will never change. Therefore, in the event of a character name being misspelled or if the character name is completely wrong or seriously misleading, a formal '''Character Name Alias''' may be assigned to the character, and this alias may be used by applications instead of the actual defective character name.<ref name="Chapter4"/> For example, {{unichar|FE18|PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRAKCET}} has the character name alias "{{sc2|PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRACKET}}" in order to mitigate the misspelling of "bracket" as {{notatypo|"brakcet"}} {{sic}} in the actual character name; {{unichar|A015|YI SYLLABLE WU}} has the character name alias {{sc2|"YI SYLLABLE ITERATION MARK"}} because, contrary to the character name, it does not have a fixed syllabic value.

In addition to character name aliases which are corrections to defective character names, some characters are assigned aliases which are alternative names or abbreviations. Five types of character name aliases are defined in the Unicode Standard:

* Correction: corrections for misspelled or seriously incorrect character names;

* Control: [[ISO 6429]] names for C0 and C1 control functions (which are not assigned character names in the Unicode Standard);

* Alternate: alternative names for some format characters (only U+{{unichar|FEFF "ZERO WIDTH NO-BREAK SPACE"}} which has the alias {{sc2|"BYTE ORDER MARK"}});

* Figment: Documented labels for some C1 control code functions which are not actual names in any standard;

* Abbreviation: Abbreviations or acronyms for control codes, format characters, spaces, and variation selectors.

All formal character name aliases follow the rules for permissible character names, and are guaranteed to be unique within both the character name alias and the character name namespaces (for this reason, the ISO 6429 name "BELL" is not defined as an alias for U+{{unichar|0007}} because U+1F514 is named "BELL"; U+0007 instead has the alias "ALERT").<ref name="Chapter4"/>

As of Unicode version 16.0, thirty-five35 formal character name aliases are defined as corrections for defective character names.<ref>{{Cite web | url=https://www.unicode.org/Public/UCD/latest/ucd/NameAliases.txt | title=UCD: Name Aliases|publisher=Unicode Consortium | work=Unicode Character Database | date=2024-04-24 }}</ref>

Apart from these normative names, '''informal names''' may be shown in the Unicode code charts. These are other commonly used names for a character, and do not have the same character restriction. These informal names are not guaranteed to be unique, and may be changed or removed in later versions of the standard.

==General Category==

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===Punctuation===

Characters have separate properties to denote they are a [[punctuation]] character. The properties all have a [[boolean value|Yes/No values]]: '''Dash''', '''Quotation_Mark''', '''Sentence_Terminal''', '''Terminal_Punctuation''. The ''Punctuation'' property refers to characters that are used to divide or structure text, and these are classified into different types based on their roles. Unicode assigns these punctuation characters specific categories.

In Unicode, Characters are assigned different properties that help in identifying their roles, such as letters, numbers, or punctuation marks. The '''Punctuation''' property refers to characters that are used to divide or structure text, and these are classified into different types based on their roles. Unicode assigns these punctuation characters specific categories.

{{main|Dash|Quotation mark glyphs#Quotation marks in Unicode|Terminal punctuation}}

===Whitespace===

{{main|Whitespace character}}

'''Whitespace''' is a commonly used concept for a typographic effect. Basically it covers invisible characters that have a spacing effect in rendered text. It includes [[Space (punctuation)|spaces]], tabs, and new line formatting controls. In Unicode, such a character has the property set "<code>WSpace=yes"</code>. In version {{Unicode version|version=16.0}}, there are 25 whitespace characters.

{{Whitespace (Unicode)|state=collapsed}}

===Casing===

The Case value is Normataivenormative in Unicode. It pertains to those scripts with uppercase (aka capital, majuscule) and the lowercase (aka small, minuscule) letters. Case-difference occurs in Adlam, Armenian, Cherokee, Coptic, Cyrillic, Deseret, Garay, Glagolitic, Greek, Khutsuri and Mkhedruli Georgian, Latin, Medefaidrin, Old Hungarian, Osage, Vithkuqi and Warang Citi scripts.

<!--(upper, lower, title, folding—both simple and full)-->

Different languages have different case mapping rules.

In Turkish, {{Unichar|0069}} corresponds to {{Unichar|0130}} instead of {{Unichar|0049}}. Similarly, {{Unichar|0049}} when corresponds to {{Unichar|0131}} instead of {{Unichar|0069}}.

In [[Nawdm]], the letter Ĥ corresponds to ɦ in lowercase instead of the usual case mappings being Ĥĥ and Ɦɦ.

In Greek, the letter sigma has different lowercase forms depending on where it is in a word. {{Unichar|03a3}} converts to {{Unichar|03c3}} if it is at the start or middle of a word, and converts to {{Unichar|03c2}} if it is at the end of a word.

In Lithuanian, the dot in lowercase i and j is preserved when followed by accents. For example: Í in lowercase is i̇́.<ref>{{Cite web|url=https://www.unicode.org/Public/UCD/latest/ucd/SpecialCasing.txt|title=Unicode Character Database: Special Casing Data|date=2024-05-10}}</ref>

Despite the existence of {{Unichar|1E9E}}, {{Unichar|00DF}} corresponds to "SS".

Unicode encodes 31 titlecase characters.

* {{Unichar|01C5}}

* {{Unichar|01C8}}

* {{Unichar|01CB}}

* {{Unichar|01F2}}

* {{Unichar|1F88}}

* {{Unichar|1F89}}

* {{Unichar|1F8A}}

* {{Unichar|1F8B}}

* {{Unichar|1F8C}}

* {{Unichar|1F8D}}

* {{Unichar|1F8E}}

* {{Unichar|1F8F}}

* {{Unichar|1F98}}

* {{Unichar|1F99}}

* {{Unichar|1F9A}}

* {{Unichar|1F9B}}

* {{Unichar|1F9C}}

* {{Unichar|1F9D}}

* {{Unichar|1F9E}}

* {{Unichar|1F9F}}

* {{Unichar|1FA8}}

* {{Unichar|1FA9}}

* {{Unichar|1FAA}}

* {{Unichar|1FAB}}

* {{Unichar|1FAC}}

* {{Unichar|1FAD}}

* {{Unichar|1FAE}}

* {{Unichar|1FAF}}

* {{Unichar|1FBC}}

* {{Unichar|1FCC}}

* {{Unichar|1FFC}}

(upper, lower, title, folding—both simple and full)

{{expand section|date=March 2022}}

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==Combining class==

{{more|Combining character}}

Some common codes:

:0 = spacing letter, symbol or modifier (e.g. {{Char|a}}, {{Char|(}}, {{Char|ʰ}})

:1 = overlay

:6 = Han reading (CJK diacritic reading marks)

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==Bidirectional writing==

Six character properties pertain to bi-directional writing: ''Bidi_Class'', ''Bidi_Control'', ''Bidi_Mirrored'', ''Bidi_Mirroring_Glyph'', ''Bidi_Paired_Bracket'' and ''Bidi_Paired_Bracket_Type''.

One of Unicode's major features is support of bi-directional (''Bidi'') text display right-to-left (R-to-L) and left-to-right (L-to-R). The Unicode Bidirectional Algorithm UAX9<ref name="UAX9">{{cite web|url=https://www.unicode.org/reports/tr9/ |title=Unicode Standard Annex #9: Unicode Bidirectional Algorithm|work=The Unicode Standard|date=2024-09-02}}</ref> describes the process of presenting text with altering script directions. For example, it enables a Hebrew quote in an English text. The ''Bidi_Character_Type'' marks a character's behaviour in directional writing. To override a direction, Unicode has defined special ''formatting control characters'' ('''Bidi-Control'''s characters). These characters can enforce a direction, and by definition only affect bi-directional writing.

Each code point has a property called '''Bidi_Class'''. It defines its behaviour in a bidirectional text as interpreted by the algorithm:

{{Bidi Class (Unicode)}}

In normal situations, the algorithm can determine the direction of a text by this character property. To control more complex Bidi situations, e.g. when an English text has a Hebrew quote, extra options are added to Unicode. Twelve12 characters have the property '''{{code|1=Bidi_Control=Yes'''}}: ALM, FSI, LRE, LRI, LRM, LRO, PDF, PDI, RLE, RLI, RLM and RLO as named in the table. These are invisible formatting control characters, only used by the algorithm and with no effect outside of bidirectional formatting.<ref name="UAX9"/> Despite the name, they are formatting characters, not control characters, and have General category "''Other, format (Cf)"'' in the Unicode definition.

Basically, the algorithm determines a sequence of characters with the same strong direction type (R-to-L ''or'' L-to-R), taking in account an overruling by the special Bidi-controls. Number strings (Weak types) are assigned a direction according to their strong environment, as are Neutral characters. Finally, the characters are displayed per a string's direction.

Two character properties are relevant to determining a mirror image of a glyph in bidirectional text: '''{{code|1=Bidi_Mirrored=Yes'''}} indicates that the glyph should be mirrored when written R-to-L. The property '''{{code|1=Bidi_Mirroring_Glyph=U+''hhhh'''''}} can then point to the mirrored character. For example, bracketsparentheses "{{char|(}}, {{char|)"}} are mirrored this way. Shaping cursive scripts such as Arabic, and mirroring glyphs that have a direction, is not part of the algorithm.

<!-- Bidi_Paired_Bracket and Bidi_Paired_Bracket_Type go here -->

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===Decimal===

Characters are classified with a '''Numeric type'''.<ref name="Chapter4"/> Characters such as fractions, subscripts, superscripts, Roman numerals, currency numerators, encircled numbers, and script-specific digits are type Numeric. They have a '''numeric value''' that can be decimal, including zero and negatives, or a vulgar fraction. If there is not such a value, as with most of the characters, the numeric type is "None".

The characters that do have a numeric value are separated in three groups: Decimal (De), Digit (Di) and Numeric (Nu, i.e. all other). "Decimal" means the character is a straight decimal digit. Only characters that are part of a contiguous encoded range 0..9 have numeric type Decimal. Other digits, like superscripts, have numeric type Digit. All numeric characters like fractions and Roman numerals end up with the type "Numeric". The intended effect is that a simple parser can use these decimal numeric values, without being distracted by say a numeric superscript or a fraction. Eighty-three CJK Ideographs that represent a number, including those used for accounting, are typed Numeric.

On the other hand, characters that could have a numeric value as a second meaning are still marked Numeric type "''None"'', and have no numeric value (""). E.g. Latin letters can be used in paragraph numbering like "II.A.1.b", but the letters "I", "A" and "b" are not numeric (type ''None'') and have no numeric value.

"None") and have no numeric value.

{{Numeric Type (Unicode)}}

===Hexadecimal digits===

[[Hexadecimal]] characters are those in the series with hexadecimal values 0...9ABCDEF0123456789ABCDEF (sixteen characters, decimal value 0–15). The character property '''Hex_Digit''' is set to Yes when a character is in such a series:

{{Hexadecimal digit (Unicode)}}

Forty-four characters are marked as ''Hex_Digit''. The ones in the Basic Latin block are also marked as '''ASCII_Hex_Digit'''.

Unicode has no separate characters for hexadecimal values. A consequence is, that when using regular characters it is not possible to determine whether hexadecimal value is intended, or even whether a value is intended at all. That should be determined at a higher level, e.g. by prepending "''0x"'' to a hexadecimal number or by context. The only feature is that Unicode can note that a sequence ''can or can not'' be a hexadecimal value.

==Block==

{{main|Unicode block}}

A '''block''' is a uniquely named, contiguous range of code points. It is identified by its first and last code point. Blocks do not [[intersection (set theory)|overlap]], nor do they extend across planes. The number of code points in each block must be a multiple of 16. A block may contain code points that are reserved, not-assigned, etc. Each character that ''is'' assigned, has a single "block name" value from the 338 names assigned as of Unicode version {{Unicode version|version=16.0}}. Unassigned code points outside of an existing block have the default value "No_block".

{{Unicode blocks|state=mw-collapsed}}

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==Age==

'''Age''' is the version of the Standardstandard in which the code point was first designated. The version number is shortened to the numbering ''major.minor''', although there more detailed version numbers are used: versions 4.0.0 and 4.0.1 both are named 4.0 as Age. Given the releases, Age can be from the range: 1.1, 2.0, 2.1, 3.0, 3.1, 3.2, 4.0, 4.1, 5.0, 5.1, 5.2, 6.0, 6.1, 6.2, 6.3, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 12.1, 13.0, 14.0, 15.0, 15.1, and 16.0.<ref name=DerivedAge>{{Cite web|url=https://www.unicode.org/Public/UCD/latest/ucd/DerivedAge.txt|title=UCD: Derived Age|publisher=Unicode Consortium|work=Unicode Character Database|date=2024-04-30}}</ref> The long values for Age begin in a V and use an underscore instead of a dot: V1_1, for example.<ref name=UAX44 /> Codepoints without a specifically assigned age value have the value "NA", with the long form "Unassigned".

==Deprecated==

Once a character has been defined, it will not be removed or reassigned.<ref>{{cite web |url=https://www.unicode.org/policies/stability_policy.html |title=Unicode Character Encoding Stability Policies |website=Unicode |date=2024-01-09 |access-date=2024-01-13 |publisher=[[Unicode Consortium]] |quote=Once a character is encoded, it will not be moved or removed.}}</ref> However, a character may be [[deprecation|deprecated]], meaning its "use is strongly discouraged".<ref>{{cite web|title=The Unicode Standard, D13 Deprecated character |url=https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-3/#G48383 |date=2024 |access-date=2024-09-13 }}</ref> As of Unicode version {{Unicode version|version=1516.10}}, the following fifteen characters are deprecated:<ref>{{cite web |url=https://www.unicode.org/Public/16.0.0/ucd/PropList.txt |title=PropList-16.0.0.txt |website=Unicode |date=2024-05-31 |access-date=2024-09-13 |publisher=[[Unicode Consortium]]}}</ref>

{|class="wikitable sortable mw-collapsible {{{state|mw-uncollapsed}}}" style="margin:0"

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|U+0627 U+065F

|اٟ

|

|-

|U+0F77

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* Line

* Sentence

{{expand section|date=January 2025}}

==Alias name==

{{main|Unicode alias names and abbreviations}}Unicode can assign '''alias names''' to code points. These names are unique over all names (including regular ones), so they can be used as identifier. There are five possible reasons to add an alias:

;1. Abbreviation

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;2. Control

:[[ISO 6429]] names for C0 and C1 control functions and similar commonly occurring names, are added as an alias to the character.

:For example, {{unichar|0008}} has the alias {{smallcaps2|BACKSPACE}}.

;3. Correction

:This is a correction for a "serious problem" in the primary character name, usually an error.

:For example, {{unichar|2118|SCRIPT CAPITAL P}} is actually a ''lowercase'' p, and so is given alias name {{smallcaps2|1=WEIERSTRASS ELLIPTIC FUNCTION}}: "actually this has the form of a lowercase calligraphic p, despite its name, and through the alias the correct spelling is added." In descriptions, with preceding symbol [[reference mark|※]].

;4. Alternate

:A widely used alternate name for a character.

:Example: {{unichar|FEFF|ZERO WIDTH NO-BREAK SPACE}} has the alternate alias {{smallcaps2|1=BYTE ORDER MARK}}.

;5. Figment

:Several documented labels for C1 control code points which were never actually approved in any standard (''[[:wikt:figment|figment]]'' =meaning "feigned, in fiction").

:For example, {{unichar|0099}} has the figment alias {{smallcaps2|1=SINGLE GRAPHIC CHARACTER INTRODUCER}}. This name is an architectural concept from early drafts of ISO/IEC 10646-1, but it was never approved andor standardized.

==External links==

*[https://www.unicode.org/reports/tr44/ Unicode Character Database], annex #44, explaining the different properties

*[https://www.unicode.org/Public/UCD/latest/ucd/UnicodeData.txt UnicodeData.txt] &ndash; a list of all Unicode characters, with their properties