1. the quality or state of being plane; flatness or levelness of a surface
2. in geometry, the quality of lying in a single plane
Usage: technical

Examples

• The planeness of the table made it ideal for writing.
• The architect checked the planeness of the foundation before construction began.
• The mirror's planeness ensures an accurate reflection.
• We tested the planeness of the wooden board with a level.
• The planeness of the surface was essential for the scientific experiment.