Ten typifying auxiliary verbs, which follow the Te form of verbs, convey the aspect of their preceding verbs after the process of grammaticalization and becoming formal verbs. In addition, the combination of a verb’s adverbial form with the verb itself constitutes a compound verb, but the verb cannot express aspect as long as it does not embrace aspect lexically. Then the question arise：Why is this derivation limited to auxiliary verbs following Te Form? And why do these auxiliary verbs acquire aspect when they follow the Te Form? The answers to these questions, according to this study, lie in the fact that the Te Form itself cannotes realis.For all the ten typifying auxiliary verbs, the structure ” Te Form＋auxiliary verb ”(V v) connotes the ideal ”doing the action of v after doing the action of V”.
This paper examines the process of gramaticalization of four auxiliary verbs with high-aspectual properties, namely Te -iru, Te -aru, Te -kuru, Te –iku, and demonstrates that the grammaticalization is due to the aspectual that Te form itself possesses.