expression, noun, noun which may take the genitive case particle 'no'
the other; the other one
Used to refer to the remaining one of two items, or the other side/party in a comparison. Often followed by は or の.
この二つの箱のうち、もう一方は空っぽだ。
Of these two boxes, the other one is empty.
彼はもう一方の手でドアを開けた。
He opened the door with his other hand.
Combination of もう (already, more) and 一方 (one side, one direction). The phrase literally means 'the other side' or 'the other one'.