The unit of study is Tirap district which lies in the south-eastern part of Arunachal Pradesh; and the languages or varieties are Nocte, Khappa, Ollo and Tutsa.

Presently, Tirap is mainly inhabited by Nocte; few villages in the district show occupancy by Nocte-Ollo and Nocte-Khappa. Noctes form the bulk of population of Tirap. This study probes the so-called sub-tribes of Nocte – Ollo and Khappa. Khappa is regarded as a literary medium of Nocte; hence the variety is used in composing songs and poetry. Ollo seeks to be an independent tribe in near future. Tutsa was regarded as a sub-tribe of Nocte, until 1991 the former got registered as an independent tribe.

The study is an attempt to lay out grammatical features based on the usage of auxiliary verbs and Be Verbs found in these languages/ varieties – Nocte, Khappa, Ollo and Tutsa; and trace how far the morphology of these languages bears the same source or show resemblances. The features taken into account here are as follows:

The study illustrates the various auxiliary verbs featuring in these languages like toŋ, nyi, daŋ jaŋ, diaŋ. It brings into focus that the existential verbs and possessive verbs are derived from posture verb toŋ ‘sit’ and verb nyi/daŋ ‘live/stay’ and je ‘exist’. These verbs provide an understanding not only of the cognates which is interestingly shared among the four; but also, the usages of content and function words shared by the same.

In addition, the study describes the Be verb hon in Ollo and Tutsa which perform inchoative functions.

The description adds not only to the understanding of rich varieties of auxiliary verbs used in these languages.; but also, source of lexical/grammatical cognates shared by these languages despite retaining their uniqueness.