Abstract:
This is a diachronic study of the words /khon/, /khuan/, /t^n/, /daj/, /na:/, and /?a:t/, which can function synchronically both as verbs and pre-nominal auxiliaries. The data used are samples of historical document, which have been published. The documents dated from the Sukhothai period to the present reign of King Rama IX. It covers the time during BE. 1926-BE. 2537. The focus of the study is the grammaticalization process which affects these six lexical items. The study reveals that these six auxillaries can be classified into 2 groups according to the types of verb from which they have developed. /khon/, /t^n/, /daj/, and /?a:t/ are grammaticalized from transitive verbs. /khuan/, and /na:/ are grammaticalized from intransitive verbs. Three types of semantic change are found to have occurred in the process. These are what Bybee et al (1994) called metaphorical extension, meaning generalization and absorption of contextual meaning. Although /khon/, /khuan/, /t^n/, /daj/, /na:/, and /?a:t/ are all grammaticalized into auxiliaries, /na:/ seems to have gone the furthest to become a recurrent component in a compounding process which changes a verb into an adjective. According to the data, /daj/ has been found as an auxiliary since the Sukhothai period. /khon/ is found occurring as aspectual auxiliary in the Ayutthaya document. /khuan/, and /t^n/ are found as auxiliaries in the document during the reign of King Rama I. /?a:t/ is not found as an auxiliary until the reign of King Rama V. For /na:/, even though its use as an episthemic auxiliary is not found in the data collected until the reign of King Rama V, the fact that it has been grammaticalized to the point of becoming a recurrent prefix-like component of a compound can be an indication that its development into a pre-nominal auxiliary could have started earlier than the other five items in this lexical set, i.e. before the Sukhothai period. The thesis concludes with an etymological description of /knon/, /khuan/, /t^n/, /daj/, /na:/ and /?a:t/