Duplicate characters in Unicode: Difference between revisions

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Formatting fixes, moved List: somewhere else because most items in the list don’t belong in the Letterlike symbols: section.
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Unicode has a number of characters specifically designated as [[Roman numerals]], as part of the ''Number Forms'' range from U+2160 to U+2183. For example, Roman 1988 ({{char|MCMLXXXVIII}}) could alternatively be written as {{char|ⅯⅭⅯⅬⅩⅩⅩⅧ}}. This range includes both uppercase and lowercase numerals, as well as pre-combined glyphs for numbers up to 12 ({{char|Ⅻ}} for {{char|XII}}), mainly intended for clock faces.
 
The pre-combined glyphs should only be used to represent the individual numbers where the use of individual glyphs is not wanted, and not to replace compounded numbers. For example, one can combine {{char|Ⅹ}} with {{char|Ⅰ}} to meanproduce Roman numeral eleven11 ({{char|ⅩⅠ}}), so U+216A ({{char|Ⅺ}}) is canonically equivalent to {{char|ⅩⅠ}}. Such characters are also referred to as composite compatibility characters or decomposable compatibility characters. Such characters would not normally have been included within the Unicode standard except for compatibility with other existing encodings (see [[Unicode compatibility characters]]). The goal was to accommodate simple translation from existing encodings into Unicode. This makes translations in the opposite direction complicated because multiple Unicode characters may map to a single character in another encoding. Without the compatibility concerns the only characters necessary would be: {{Char|Ⅰ}}, {{Char|Ⅴ}}, {{Char|Ⅹ}}, {{Char|Ⅼ}}, {{Char|Ⅽ}}, {{Char|Ⅾ}}, {{Char|Ⅿ}}, {{Char|ⅰ}}, {{Char|ⅴ}}, {{Char|ⅹ}}, {{Char|ⅼ}}, {{Char|ⅽ}}, {{Char|ⅾ}}, {{Char|ⅿ}}, {{Char|ↀ}}, {{Char|ↁ}}, {{Char|ↂ}}, {{Char|ↇ}}, {{Char|ↈ}}, and {{Char|Ↄ}}; all other Roman numerals can be composed from these.
 
=== Arabic presentation forms ===
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The contextual-form characters are not recommended for general use.
 
There are also compatibility Arabic ligatures encoded such as {{unichar|FDF2}} and {{unichar|FDFD}}.
 
=== Hebrew presentation forms ===