Tatar
Tatar has a number of vowels which are written with ambiguous letters that are normally resolved by context, but which are resolved by discontinuous digraphs when context is not sufficient. These ambiguous vowel letters are е, front /je/ or back /jɤ/, ю, front /jy/ or back /ju/; and я, front /jæ/ or back /ja/. They interact with the ambiguous consonant letters к, velar /k/ or uvular /q/, and г, velar /ɡ/ or uvular /ʁ/.
In general, velar consonants occur before front vowels and uvular consonants before back vowels, so it is frequently not necessary to specify these values in the orthography. However, this is not always the case. A uvular followed by a front vowel, as in /qærdæʃ/ "kinsman", for example, is written with the corresponding back vowel to specify the uvular value: кардәш. The front value of а is required by vowel harmony with the following front vowel ә, so this spelling is unambiguous.
If, however, the proper value of the vowel is not recoverable by through vowel harmony, then the letter ь /ʔ/ is added at the end of the syllable, as in шагыйрь /ʃaʁir/ "poet". That is, /i/ is written with a ы rather than a и to show that the г is pronounced /ʁ/ rather than /ɡ/, then the ь is added to show that the ы is pronounced as if it were a и, so the discontinuous digraph ы...ь is used here to write the vowel /i/. This strategy is also followed with the ambiguous letters е, ю, and я in final syllables, for instance in юнь /jyn/ cheap. That is, the discontinuous digraphs е...ь, ю...ь, я...ь are used for /j/ plus the front vowels /e, y, æ/.
Exceptional final-syllable velars and uvulars, however, are written with simple digraphs, with ь for velars and ъ for uvulars: пакь /pak/ pure, вәгъдә /wæʁdæ/ promise.
Read more about this topic: Cyrillic Digraphs