Mongolian I: The Neutral Vowel

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.