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. The second book focuses on etymology, morphology, and syntax. It defines how words are formed, classified into tinai (categories), and how they interact in a sentence.
Tholkappiyar categorizes the Tamil landscape into five geographical regions (), each associated with a specific human emotion tolkappiyam
The name Tolkappiyam is derived from the combination of two words: (ancient/old) and "Kappiyam" (literature/treatise). Thus, it literally translates to "The Ancient Treatise." It is attributed to Tholkappiyar , a sage who is said to have been a disciple of Agastya, the father of Tamil grammar. While legend suggests that Agastya authored the first grammar, the Tolkappiyam is the earliest text that has survived the ravages of time, making it the de facto origin point for Tamil grammatical studies. This classification is scientifically precise