The Dadun Bonan language has gə developed from the numeral "one", which seldom appear in discourse. While previous studies describe it as a singular suffix, analysis of these studies are insufficient because (1)it is syntactically an independend word, but phonologically attaches to a preposed word, and (2)it can be postposed not only to common nouns, but also to numeral, plural nouns and so on.

This paper aims to show characteristics of gə as follows.

1. Morpheme Classification: Clitic

2. Positions: Postposed to nominative or zero-accusative forms of lower in animacy, such as common nouns etc, while it is not postposed to higher in animacy, such as person pronouns, demonstrative pronouns and proper names.

3. Phonology: Give Pominence to the proposed lower in animacy.

4. Semantic Function: Exclusivity

5. Discourse Function: Discourse topic marker, which is used as (a)topic-introducing or scene-setting at the opening of discourse, (b)temporary topic-shift at the middle of discourse, (c)topic-introducing in a new scene at the middle of discourse, (d)topic- or scene-concluding at the closing of discourse, (e)repetition of a topic which has just been introduced in the immediately prior discourse.