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Unicode has a certain amount of duplication of characters. These are pairs of single Unicode code points that are canonically equivalent. The reason for this are compatibility issues with legacy systems. Unless two characters are canonically equivalent, they are not "duplicate" in the narrow sense. There is, however, room for disagreement on whether two Unicode characters really encode the same grapheme in cases such as the "micro sign" µ vs. the Greek μ. This should be clearly distinguished from Unicode characters that are rendered as identical glyphs or near-identical glyphs (homoglyphs), either because they are historically cognate (such as Greek Η vs. Latin H) or because of coincidental similarity (such as Greek Ρ vs. Latin P, or Greek Η vs. Cyrillic Н, or the following homoglyphs quadruplet: astronomical symbol for "Sun" ☉, "circled dot operator" ⊙, the Gothic letter 𐍈, the IPA symbol for a bilabial click ). ==Duplicate vs. derived character== Unicode aims at encoding graphemes, not individual "meanings" ("semantics") of graphemes, and not glyphs. It is a matter of case-by-case judgement whether such characters should receive separate encoding when used in technical contexts, e.g. Greek letters used as mathematical symbols: thus, the choice to have a "micro- sign" µ separate from Greek μ, but not a "Mega sign" separate from Latin M was a pragmatic decision by Unicode consortium for historical reasons (compatibility with Latin-1 which included a micro sign). Technically µ and μ are not duplicate characters in that the consortium viewed these symbols as distinct characters (while it regarded M for "Mega" and Latin M as one and the same character). Note that merely having different "meanings" is not sufficient grounds to split a grapheme into several characters: Thus, the acute accent may represent word accent in Welsh or Swedish, it may express vowel quality in French, and it may express vowel length in Hungarian, Icelandic or Irish. Since all these languages are written in the same script, namely Latin script, the acute accent in its various meanings is considered one and the same combining diacritic character (U+0301), as well as the accented letter é is the same character in French and Hungarian. There is a separate "combining diacritic acute tone mark" at U+0341 for the romanization of tone languages, one important difference between the two being that in a language like French, the acute accent can replace the dot over the lowercase i, whereas in a language like Vietnamese, the acute tone mark is added above the dot. Diacritic signs for alphabets considered independent may be encoded separately, such as the acute ("tonos") for the Greek alphabet at U+0384, and for the Armenian alphabet at U+055B. Some Cyrillic-based alphabets (such as Russian) also use the acute accent, but there is no "Cyrillic acute" encoded separately and U+301 should be used for Cyrillic as well as Latin (see Cyrillic characters in Unicode). The point that the same grapheme can have many "meanings" is even more obvious considering e.g. the letter U, which has entirely different phonemic referents in the various languages that use it in their orthographies (English etc., French , German , etc., not to mention various uses of U as a symbol). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Duplicate characters in Unicode」の詳細全文を読む スポンサード リンク
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