(Phonetics) Uttered, as an element of speech, with tone or proper vocal sound, as distinguished from mere breath sound; intonated; voiced; vocal; tonic; the opposite of nonvocal, or surd; said of the vowels, semivowels, liquids, and nasals, and particularly of the consonants b, d, g hard, v, etc., as compared with their cognates p, t, k, f, etc., which are called nonvocal, surd, or aspirate.
... was the original form in Sanskrit; and here no Sanskrit scholar would hesitate for one moment between tat and tad. Whatever the origin of tat may have been, it is quite certain that Sanskrit knows only of tad, never of tat. There are various ways of testing the original surd or sonant nature of final consonants in Sanskrit. One of the safest seems to me to see how those consonants behave before taddhita or secondary suffixes, which require no change in the final consonant of the base. Thus before the suffix ya (called cha by P{n}ini) the final consonant ... — Chips from a German Workshop - Volume IV - Essays chiefly on the Science of Language • Max Muller
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