The waning phase of the moon - the second fifteen phases / tithis (Phases of the Moon) comprises the Krishna paksha, where the moon diminishes and disappears on the new moon day. This period is called
Theipirai tithi-kkal. The fifteenth tithi (phase/ waning phase) is the new-moon day, termed as Amavasai or Amavasya (sanskrit).
The names of the Theipirai tithis are: Prathamai (Pratipada), Dvitiyai, Tritiyai, Chaturthi, Panchami, Shasthi, Saptami, Ashtami, Navami, Dasami, Ekadasi, Dvadasi, Trayodasi and Chaturdasi. These repeat, beginning with Prathama at the beginning of each paksha. The 15th tithi is new-moon day, Amavasyai.