Later medieval commentaries—most notably by (c. 12th century CE) and Senavaraiyar (c. 14th century CE)—preserved the text when palm-leaf manuscripts began to decay. Ilampuranar’s commentary is especially critical because it quotes older, now-lost texts and provides glosses on social customs that had become obscure.
The text classifies the land into five ecological zones, each associated with specific moods, deities, and lifestyles. For example, (mountains) is linked to the union of lovers and the deity (wasteland) signifies separation and the goddess Emotional Theory ( tolkappiyam
This classification is scientifically precise. He details the origin of sounds based on the human vocal apparatus—throat, palate, teeth, lips, and nose. He also establishes the concept of strict distinctiveness between "native" Tamil sounds and "borrowed" sounds (referred to as Vada Mozhi or Northern language, implying Sanskrit), setting the rules for how loanwords should be adapted into Tamil phonetics. Later medieval commentaries—most notably by (c