Ostraka of Xanthippos Arriphronos, father of Perikles, dated to ca. 484 B.C. Athenian Agora Excavations. For more information, click the image. Key Terms and Concepts LABIALS DENTALS PALATALS STOP CONSONANTS UNVOICED STOPS VOICED STOPS ASPIRATED STOPS THE TROUBLE WITH SIGMA NASALS LIQUIDS DOUBLE CONSONANT Chapter Navigation Key Terms and Concepts Labials, Dentals, and Palatals The Trouble with Sigma Nasals, Liquids, and Zeta The Consonant Chart and The Full Alphabet Exercises 2 Book Nav Exercises 1 Labials, Dentals, and Palatals