Mongolian Ka: A Velar for Words From Elsewhere

Ka writes a velar stop distinct from the harmony governed pair in the native part of the alphabet, and it is the twenty-seventh letter, the second of the ten added for foreign sounds. Unicode encodes it at U+183A. The native alphabet already has two velars, one for back class words and one for front class words, and the choice between them is not free: it follows from the vowels of the word. That arrangement works perfectly for Mongolian and fails immediately for a borrowed word, which arrives with a velar of its own and no harmony class to assign it to.

A separate letter standing outside the harmony solves the problem by refusing to participate in it. The same logic produced the aspirated velar that follows and the fricative further along: each covers a velar distinction that foreign vocabulary requires and Mongolian does not make. Chinese loanwords are the main reason this particular letter exists. A reader meeting it knows at once that the word is not native and knows roughly where to look for it, which is the incidental benefit of keeping the added letters separate from the inherited ones instead of overloading the existing shapes. The alternative would have been to write borrowed velars with whichever native letter the surrounding vowels happened to demand, which would have made the harmony class of a foreign word into a spelling decision and produced a different written form of the same word in different contexts. Adding a letter was the cheaper answer.