The language of medieval Tamil demonstrates many linguistic forms that are unique to all of the bhakti literatures of the medieval period, which extends roughly from the sixth century C.E. to the thirteenth century C.E.; also it contains within it a number of grammatical features that are very common in modern Tamil, but are not found in the language of old Tamil. This presupposes that many of the linguistic features that evolved during the medieval period underlay the development of many of the new grammatical forms and lexical items as they exist in modern Tamil. In this respect, this dissertation serves two significant purposes in the field of Tamil studies: (a) it provides a detailed linguistic analysis, from a synchronic point of view, of the language of Tirumantiram, one of the twelve major Saiva canons of the medieval period, and (b) it makes a systematic comparative study, from a diachronic point of view, of some of the verbal and nominal forms as they occur in the language of Tirumantiram, linking them to developments in the other two stages of Tamil, namely old and modern Tamil. The linguistic changes that took place between the medieval and post-medieval period, in large part, are responsible for both the simplification and enlargement of the language of modern Tamil. These linguistic changes that occurred in Tamil are discussed in detail in this dissertation with appropriate examples drawn from the language of the three stages of Tamil, namely old, medieval and modern.