Mongolian Ang and the Shape of the Native Word

An alphabet quietly records the shape of the words it was built for. Mongolian permits no word to begin with the velar nasal, none to begin with r, and none to begin with the voiceless bilabial stop, and each of those restrictions leaves a trace in how the script is used. A word beginning with one of them is a borrowing, and a reader can tell as much before knowing what the word means. That makes the letters at these positions useful diagnostics: an initial r or p in a Mongolian text is a flag that the word arrived from Tibetan, Sanskrit, Chinese, Russian or elsewhere. Restrictions of this kind are called phonotactic, and they differ sharply between languages.

English forbids an initial velar nasal too, which is why English speakers find the sound easy at the end of a word and hard at the start of one, while many languages of Southeast Asia and Africa allow it without difficulty. When a script is borrowed across such a boundary the fit is never exact, and the gaps show up in exactly this way. The traditional Mongolian alphabet was extended at its end with ten letters for sounds met in foreign vocabulary, which is the same problem solved from the other direction: not what the language forbids at the start of a word, but what it does not contain at all.