plane and plain

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). Also simple as in apparent.
Plain is an adjective in these examples. An expanse of level and low land. Plain is a noun in these examples.


The word plane has several meanings:

An airplane.
A flat surface (especially in mathematics) . A tool for smoothing or shaping wood (i.e., a carpenter's plane).

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

To travel on the surface of water.

A Quick Test

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.

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See Also

What are adjectives? What are nouns? What are verbs? List of easily confused words