Grammar Monster
Grammar Monster

plane and plain - the difference

The Quick Answer
Plane usually means an airplane, a flat surface or a tool for shaving wood.
Plain usually means simple or an expanse of lowland.

The words plane and plain have several meanings. Unfortunately, both have a meaning relating to flatness, and this is often the source of confusion.


The word plain has several meanings:

Simple (i.e., not elaborate).
  • a plain girl
  • a plain cake
  • a plain colour
Also simple as in apparent.
  • It is plain to see.
  • It seems quite plain to me.

Plain is an adjective in these examples. An expanse of level and low land.
  • The Russian Plain.
  • I joined the Chinese farmers as they attempted to drive the yaks across the plain in western China.
Plain is a noun in these examples.


The word plane has several meanings:

An airplane.
  • What time is your plane?

A flat surface (especially in mathematics) .
  • In a 3D space, a plane can be defined by specifying a point and a normal vector to the plane.
  • Also means a level (usually figurative).

  • I was hoping for a conversion on a higher plane.
A tool for smoothing or shaping wood (i.e., a carpenter's plane).

Also the verb to plane (i.e., to shape wood).

  • Can you plane a few inches off the top of the door?
To travel on the surface of water.
  • The car hit the puddle and planed straight into the back of the lorry.
    (also known as to aquaplane)
Quick Test
Top Tip

Planes Are above Ground

Confusion arises mostly between plain meaning expanse of lowland and plane meaning a flat surface or a level.

A plain (lowland) is always on the ground. A plane (a surface or a level) is nearly always above the an airplane.

Therefore, if it's above the ground, it's almost certainly plane.