qiáo shé yīn
retroflex
consonants zh, ch, sh, r produced on the back of the tongue
píng shé yīn
alveolar
consonants z, c, s produced with the tip of the tongue on the alveolar ridge
qiào shé yīn
retroflex sound (e.g. in Mandarin zh, ch, sh, r)
shé yīn
coronal consonants of Middle Chinese