宋高僧傳 3.43

3.43

第四、麁言細語者。「聲明」中，一「蘇漫多」，謂汎爾平語言辭也。二「彥底多」，謂典正言辭也。佛說法多依「蘇漫多」，意住於義，不依於文，又被一切故，若「彥底多」，非諸類所能解。故亦名「全聲」者，則言音分明典正，此細語也。「半聲」者，則言音不分明而訛僻，此麁語也。

Fourth, coarse speech and fine speech: within linguistic science (śabdavidyā), the first is subanta, referring to ordinary, colloquial speech and expressions. The second is tiṅanta, referring to classical, correct speech and expressions. The Buddha's preaching of the Dharma mostly relied upon subanta, his intention abiding in the meaning and not relying on the letter, and also because it addressed everyone; whereas tiṅanta could not be understood by all kinds of beings. Therefore, what is also called 'full sound' is when the pronunciation is distinct, classical, and correct; this is fine speech. 'Half sound' is when the pronunciation is indistinct and corrupted or vernacular; this is coarse speech.