I-dot

The Turkish alphabet, which is a variant of the Latin alphabet, includes two distinct versions of the letter I, one dotted and the other dotless.

The dotless I, I ı, denotes the close back unrounded vowel sound (/ɯ/). Neither the upper nor the lower case version has a dot.

The dotted İ, İ i, denotes the close front unrounded vowel sound (/i/). Both the upper and lower case versions have a dot.

Examples:

In contrast, the letter j does not have this distinction, with a dot only on the lower case character: J j.

In scholarly writing on Turkic languages, ï is sometimes used for /ɯ/.

In some fonts, if the lowercase letters fi are placed adjacently, the dot-like upper end of the f would fall inconveniently close to the dot of the i, and therefore a ligature glyph is provided with the top of the f extended to serve as the dot of the i. A similar ligature for ffi is also possible. Since the unligatured forms are unattractive and the ligatures make the i dotless, such fonts are not appropriate for use in a Turkish setting. However, the fi ligatures of some fonts do not merge the letters and instead space them next to each other, with the dot on the i remaining. Such fonts are appropriate for Turkish, but the writer must be careful to be consistent in the use of ligatures.

In normal typography, when lower case i is combined with other diacritics, the dot is generally removed before the diacritic is added; however, Unicode still lists the equivalent combining sequences as including the dotted i, since logically it is the normal dotted i character that is being modified.

Most Unicode software uppercases ı to I and lowercases İ to i, but, unless specifically set up for Turkish, it lowercases I to i and uppercases i to I. Thus uppercasing then lowercasing, or vice versa, changes the letters.

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