Diaeresis

In linguistics, a diaeresis or dieresis (AE) (from Greek ???????? (diaerein), to divide) is the modification of a syllable by distinctly pronouncing one of its vowels. The diacritic mark composed of two small dots ( ¨ ) placed over a vowel to indicate this modification is also called a diaeresis. (In the case of an "i", it replaces the original dot.)

How to produce the characters on computers

The ISO 8859-1 character encoding includes the letters ä, ë, ï, ö, ü, and their respective capital forms, as well as ÿ in lower case only (? was added in the revised edition, ISO 8859-15). Dozens of more letters with the diaeresis are available in Unicode. Unicode also provides the diaeresis as a combining character U+0308. Unicode treats the umlaut as the same diacritic mark as diaeresis, and does not encode separate characters for the same letter with umlaut and with diaeresis. In those cases where umlauts must be distinguished from diaeresis, the special character U+034F COMBINING GRAPHEME JOINER (CGJ) can be used:

Related Topics:
ISO 8859-1 - Capital - Lower case - ISO 8859-15 - Unicode - Combining character

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:For diaeresis: X + CGJ + COMBINING DIAERESIS (e.g. a͏̈)

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:For umlauts: X + COMBINING DIAERESIS (e.g. ä)

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It is then up to the user agent and typeface being used to provide meaningful distinction between the two characters.

Related Topics:
User agent - Typeface

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The HTML entities for these characters all end in uml; e.g. ä = ä. These entities however use the Unicode diaeresis codepoints when rendered.

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TeX also allows double dots to be placed over letters in math mode, using "ddot{}", or outside of math mode, with the " control sequence:

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: mathrm{ddot{a}ddot{b}ddot{c}ddot{d}ddot{e}ddot{A}ddot{B}ddot{C}ddot{D}ddot{E}}

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However this will give the diaeresis-style dots that are too far above the letter's body for good typographical umlauts. TeX's "german" package should be used if possible: it adds the " control sequence (without backslash) which gives nice umlauts.

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On the Apple Macintosh, the diaeresis is produced with the keystroke Option+U, followed by the character to receive the diaeresis.

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Using Microsoft Word, the diaeresis is produced by pressing Ctrl+Shift+:, then the letter.

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