A plane extends in two dimensions.
In terms of how it is written, you might say:
- A plane extends in two dimensions: length and width.
- A plane is a flat, two-dimensional surface that can be defined by three points that are not collinear.
Mathematically, you might express a plane in a Cartesian coordinate system with an equation like \( Ax + By + C = 0 \), where \( A \), \( B \), and \( C \) are constants.