noun which may take the genitive case particle 'no'
coplanar; in the same plane; flush; even with
Technical term used in geometry, engineering, and design to describe objects lying in the same plane or surfaces that are level with each other. Often appears as 同一平面上に.
These points are coplanar.
Install the shelf surface flush with the wall.
Compound of 同一 (same) + 平面 (plane) + 上 (on). The exact historical derivation is uncertain, but the term is a straightforward technical compound.