7th Grade · Geometry
Plane
7.G.A.3
Definition
A flat, two-dimensional surface that extends infinitely in all directions. Defined by any three non-collinear points. Planes have no thickness.
Examples
- A table surface or calm lake approximates a plane, but has edges and imperfections.
- A plane is a mathematical abstraction — it doesn't actually exist in the physical world.
Key rule
A plane is flat, infinite, two-dimensional, and defined by three non-collinear points.
Memory hook
Flat and infinite in every direction.