Initially in French and also in Afrikaans, Catalan, Dutch, Galician, Southern Sami, Welsh, and occasionally English, ⟨ï⟩ is used when ⟨i⟩ follows another vowel and indicates hiatus in the pronunciation of such a word. It indicates that the two vowels are pronounced in separate syllables, rather than together as a diphthong or digraph. For example, French maïs (IPA: [ma.is], maize); without the diaeresis, the ⟨i⟩ is part of the digraph ⟨ai⟩: mais (IPA: [mɛ], but). The letter is also used in the same context in Dutch, as in Oekraïne (pronounced [ukraːˈinə], Ukraine), and English naïve (// or //).
In German and Hungarian, ï or I-umlaut does not belong to the alphabet.
In scholarly writing on Turkic languages, ⟨ï⟩ is sometimes used to write the close back unrounded vowel /ɯ/, which, in the standard modern Turkish alphabet, is written as the dotless i ⟨ı⟩. The back neutral vowel reconstructed in Proto-Mongolic is sometimes written ⟨ï⟩.
It is also a transliteration of the rune ᛇ.
Lowercase ï occurs in the sequence ï»¿, which is the Unicode byte order mark in UTF-8 misinterpreted as ISO-8859-1 or CP1252 (both common encodings in software configured for English-language users). Thus, it tends to indicate that any following mojibake can be corrected by reinterpreting the data as UTF-8.
|Unicode name||LATIN CAPITAL LETTER I WITH DIAERESIS||LATIN SMALL LETTER I WITH DIAERESIS|
|UTF-8||195 143||C3 8F||195 175||C3 AF|
|Numeric character reference||Ï
|Named character reference||Ï||ï|