Mongolian Ya ᠶ

Ya writes the palatal glide, the sound English spells y at the start of a word, and it is the twenty-second letter of the alphabet. It is historically the same sign as the vowel i, which is why the two share written shapes and why alphabet charts frequently discuss them together. A glide is a vowel doing a consonant's work, articulated in the same place as the close front vowel but occupying the position in a syllable that a consonant occupies, and many writing systems accordingly use one letter for both or derive one from the other. Latin did exactly this before i and j were separated, and Greek and the Semitic alphabets show the same pattern in their own way.

Unicode encodes ya at U+1836. In Mongolian the two functions are kept apart in the alphabet's list but not always in the writing, so a run of teeth and strokes on the spine may be read as a vowel or as a glide depending on the word and its syllable structure. As with the other ambiguities in this script, the resolution comes from knowing the language, and the alphabet is content to leave it there. The glide is native, common and unrestricted in position, so unlike the trill or the voiceless bilabial stop it tells a reader nothing about where a word came from. Its shared history with the vowel i is the reason a table lining up Mongolian letters against their Sogdian and Aramaic ancestors will show two Mongolian letters converging on one earlier sign at this point, and the same happens again where the rounded vowels meet the labial glide. Convergences of that kind are the normal residue of an alphabet that has been handed from one language to another several times without ever being redesigned.

Alphabets are usually taught as a list of vowels and a list of consonants, and the glides are where that tidy division fails. The palatal glide and the labial glide are made like vowels and behave like consonants, and every alphabet has to decide what to do with them. The Semitic abjads from which this script ultimately descends used the same letters for both jobs, writing the glides as consonants and later pressing the same signs into service as vowel letters, which is how the ancestors of these Mongolian letters acquired their vowel readings in the first place. The vowel i and the palatal glide are one sign in that history; the rounded vowels and the labial glide are another.

Mongolian inherited the arrangement and kept it, listing four vowels and a glide where the ancestry had one letter, and writing them with shapes that overlap accordingly. It is worth knowing this when comparing the Mongolian alphabet with its relatives, because a table that lines up the letters one to one will always break at the glides, and the break is not an error in the table. It is the record of one sign being asked to do several jobs over two thousand years. The same reasoning explains why the alphabet's list and the alphabet's shapes do not correspond one to one. A recited list names the letters the tradition counts; the shapes on a page record only what the tradition thought worth distinguishing, and the two have never been the same inventory.