Comments: PAT *śǝ, attested only with preverbs, cf. Abkh. ája-s-ra 'to pass', a-ḳǝ́l-s-ra 'to pass through, crawl through', a-bž́ǝ́-s-ra 'to pass by'; Abaz. ḳǝl-s-ra,bž́ǝ-s-ra id.; Bzyb. ā́-ś-ḳ́a-ra 'to move (here), come (here)', a-na-ś-ḳ́a-ra 'to move (there), get away'. PAK *na-sǝ- 'come, reach (there)', *q:a-sǝ- (Ad., Kab. q:a-sǝ-n) 'come, reach (here)'.
We must notice that in PAK probably a contamination of two PWC roots took place: on one hand, PAK *na-sǝ- and *q:a-sǝ- are exact formal matches of Bzyb. a-na-ś- and ā-ś- (see above); on the other hand, semantically they also match perfectly Abkh. a-na-ʒa- 'to reach (there)' and ā-ʒa- 'to reach (here)' (see under PWC *ʒV). The derived postposition PAK *-nasǝ 'until' is also exactly matching Abkh. -nʒa and Ub. -ōnʒa. See Dumézil 1932, 75, 250-251; Shagirov 1, 279-280.