adjective belonging to one shoulder, on or with one shoulder; only in phṛase ekaṃsaṃ uttarāsangaṃ karoti to arrange the upper robe over one shoulder (the left) Vin.i.46; Vin.ii.188 & passim.
eka + aṃsa1
“one part or point”, i.e. one-pointedness, definiteness; affirmation, certainty absoluteness DN.i.153; AN.ii.46; Snp.427, Snp.1027; Ja.iii.224 (ekaṃsatthe nipāto for “nūna”); Snp-a.414 (˚vacana for “taggha”)
■ Opp. an˚; Mil.225
■ instr. ekaṃsena as adv. for certain, absolutely, definitely, inevitably DN.i.122 DN.i.161, DN.i.162; MN.i.393; SN.iv.326; AN.v.190; Ja.i.150; Ja.iii.224; Pv-a.11.
eka + aṃsa1 or better aṃsa2