Mongolian I ᠢ

I writes the close front vowel and is the third letter of the alphabet, but its interest lies in what it does not do. It is neutral to the vowel harmony, which means it appears in words of the back class and words of the front class alike without disturbing either. Where every other vowel commits a word to one series, i commits it to nothing, and a word whose only vowel is i has to be assigned to a class by other evidence, usually by the form its suffixes take. That makes i the exception that reveals the rule: the harmony is a real constraint on the other vowels precisely because this one is exempt from it.

In writing, i is a tooth followed by a further stroke, and inside a word it is one of the shapes most easily confused with its neighbours, since a run of teeth on the spine can be read several ways until the word is recognised. The same shape does duty for the glide written y at the start of a word, and the two letters are historically the same sign, which is why the alphabet keeps them adjacent in some arrangements. Unicode encodes i at U+1822. In the sequence of vowels the alphabet recites, i sits between the two harmony classes rather than in either, which is exactly where its behaviour puts it.

Traditional Mongolian writing asks more of its reader than most alphabets do. Several distinct letters share a written shape, and the reader resolves them from the word rather than from the page. The vowel i is one of the shapes involved, since a tooth followed by a stroke can be read more than one way in a run of similar strokes. The rounded vowels are written with one shape for two sounds. The two dental stops are not consistently kept apart. The nasal is distinguished from a vowel by a dot that ordinary handwriting often omits. None of this is carelessness, and it is worth saying so plainly, because a script that looks underspecified to an outsider is usually well specified for the language it serves.

A fluent reader of Mongolian is not decoding letter by letter; the vocabulary is finite, the harmony narrows the possibilities sharply, and the word is recognised as a whole. The cost falls on other readers: on learners, on scholars reading unfamiliar names, and on machines. It is one of the reasons the Mongolian People's Republic adopted a Cyrillic orthography in the twentieth century, and one of the reasons digital text in the traditional script has needed a good deal of engineering to render correctly. The ambiguity is a genuine property of the writing system, not a fault in any particular copy of it.