Plane

A plane surface is a flat surface, and any distinct flat surface within a painting or sculpture can be referred to as a plane

Pablo Picasso, ‘Head of a Woman’ 1924 — Pablo Picasso
Head of a Woman 1924
Tate
© Succession Picasso/DACS 2020

Jasper Johns, ‘Dancers on a Plane’ 1980–1 — Jasper Johns
Dancers on a Plane 1980–1
Tate
© Jasper Johns

Dame Barbara Hepworth, ‘Ball, Plane and Hole’ 1936 — Dame Barbara Hepworth
Ball, Plane and Hole 1936
Tate
© Bowness

The flat patches seen in cubist paintings are often referred to as planes, and geometric abstract artists refer frequently to planes in discussing their work.