also: うわかわ
noun, noun which may take the genitive case particle 'no'
upper side; top surface
Refers to the upper side or surface of something, often contrasted with 下側 (underside). Can be used as a noun or with の to modify another noun.
箱の上側にラベルを貼ってください。
Please put the label on the top side of the box.
上側の引き出しに書類が入っています。
The documents are in the upper drawer.
Compound of 上 (うわ, 'upper') and 側 (がわ, 'side'). The reading うわかわ is a variant, but うわがわ is more common.