Mongolian Wa: The Labial Glide

Wa writes the labial glide, transliterated w or v depending on the system in use, and it is the twenty-fifth and last of the letters inherited as the native core of the alphabet. The sound is met chiefly in words taken from other languages, which puts this letter in the same category as the voiceless bilabial stop and the trill: present in the alphabet, present in the language, and a strong hint of foreign vocabulary when it appears. Unicode encodes wa at U+1838. After it the alphabet turns to letters supplied specifically for foreign sounds, ten of them, so this letter marks the seam between the inherited script and everything added to it.

Historically the labial glide belongs with the rounded vowels, since all of them descend from a single letter of the Aramaic abjad which wrote the glide and was pressed into service for the vowels. That is why the shapes overlap and why a table aligning Mongolian with its ancestors always shows several Mongolian letters converging on one earlier sign. The transliteration of the letter varies more than most: w preserves the historical value, v often reflects modern pronunciation in loanwords, and different scholarly systems choose differently.