O. R. Radhakrishnan in his note “Tolkāppiyam on Intervocalic Stops” published in the Indo-Iranian Journal (Vol. IX, No.3 , pp. 209-210) points out that Tolkāppiyar has used the term icaittal in the sense of “voicing” and uyirttal in the sense of “breathing". To quote him fully, “Note that icai and uyir, the stems in the two terms mentioned above, also mean respectively ‘music’ and ‘life', for which voicing and breathing are indispensable. When Tolkāppiyam describes sounds that are voiced it employs the term icai; but when it describes sounds that are voiceless it employs the term uyirttal. According to Tolkāppiyam the vowels (Sūtra 84), the nasals (Sūtra 100), and the liquids (Sūtra 99) are voiced; the stops are breathed (Sūtra 17), except when they are preceded by nasals (Sūtra 25)” (p. 210).