plane

¹ American  

[pleyn] / pleɪn /

noun

1. a flat or level surface.

2. Geometry. a surface generated by a straight line moving at a constant velocity with respect to a fixed point.

3. Fine Arts. an area of a two-dimensional surface having determinate extension and spatial direction or position.

   oblique plane; horizontal plane.

4. a level of dignity, character, existence, development, or the like.

   a high moral plane.

   Synonyms:

   stage, stratum

5. Aeronautics.

   1. an airplane or a hydroplane.

      to take a plane to Dallas.

   2. a thin, flat or curved, extended section of an airplane or a hydroplane, affording a supporting surface.

6. Architecture. a longitudinal section through the axis of a column.

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adjective

1. flat or level, as a surface.

   Synonyms:

   flush, even, smooth

2. of or relating to planes or plane figures.

verb (used without object)

planed, planing

1. to glide or soar.

2. (of a boat) to rise partly out of the water when moving at high speed.

3. Informal. to fly or travel in an airplane.

   We'll drive to Detroit and plane to Los Angeles.

plane ² American  

[pleyn] / pleɪn /

noun

1. Carpentry. any of various woodworking instruments for paring, truing, or smoothing, or for forming moldings, chamfers, rabbets, grooves, etc., by means of an inclined, adjustable blade moved along and against the piece being worked.

2. a trowellike tool for smoothing the surface of clay in a brick mold.

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verb (used with object)

planed, planing

1. to smooth or dress with or as if with a plane or a planer.

2. to remove by or as if by means of a plane (usually followed by away oroff ).

verb (used without object)

planed, planing

1. to work with a plane.

2. to function as a plane.

plane ³ American  

[pleyn] / pleɪn /

noun

1. plane tree.

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plane ¹ British  

/ pleɪn /

noun

1. maths a flat surface in which a straight line joining any two of its points lies entirely on that surface

2. a flat or level surface

3. a level of existence, performance, attainment, etc

4. 1. short for aeroplane

   2. a wing or supporting surface of an aircraft or hydroplane

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adjective

1. level or flat

2. maths (of a curve, figure, etc) lying entirely in one plane

verb

1. to fly without moving wings or using engines; glide

2. (of a boat) to rise partly and skim over the water when moving at a certain speed

3. to travel by aeroplane

plane ² British  

/ pleɪn /

noun

1. a tool with an adjustable sharpened steel blade set obliquely in a wooden or iron body, for levelling or smoothing timber surfaces, cutting mouldings or grooves, etc

2. a flat tool, usually metal, for smoothing the surface of clay or plaster in a mould

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verb

1. to level, smooth, or cut (timber, wooden articles, etc) using a plane or similar tool

2. (often foll by off) to remove using a plane

plane ³ British  

/ pleɪn /

noun

1. See plane tree

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plane Scientific  

/ plān /

1. A two-dimensional surface, any two of whose points can be joined by a straight line that lies entirely in the surface.

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1. Lying in a plane:

plane Cultural  

1. A geometrical location having only two dimensions — length and width (no height). (See coordinates and plane geometry.)

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Usage

What does plane mean? In geometry, a plane  is a flat, two-dimensional surface with an infinite height and width. It’s one of the basic concepts of geometry. Think of a flat sheet of paper. A physical sheet of paper has three dimensions: length, width, and (a small) height. If that sheet of paper had zero height and its length and width extended forever, it would be a plane. Obviously, such a shape is theoretical—it’s used as a basis for geometric calculations. A plane is one of several basic concepts students need to begin to understand geometry. Another is a point. Unlike a plane, it has no dimensions, such as length or width. It is found by using coordinates. A third concept is a line. Like a plane, a line also extends forever but only in two directions. Understanding what a plane is matters because angles and two-dimensional shapes, such as squares, triangles, and circles, are represented as points, lines, and line segments on a plane. It also helps you understand three-dimensional space and three-dimensional objects, which have height as well as length and width. Plane has several other meanings, some of which have different roots. More generally, it can refer to any flat or level surface.

Other Word Forms

• planeness
  noun

Etymology

Origin of plane¹

First recorded in 1400–50 plane ¹ ( for def. 9 ) (in the sense “to soar”); 1640–50 for noun and adjective senses; (noun) from Latin plānum “flat surface” (noun use of plānus “flat”); (adjective) from Latin plānus; first used to distinguish the geometrical senses formerly belonging to plain ¹; plane ¹ ( in def. 5 ), shortened form of airplane, aeroplane, or hydroplane; (verb) late Middle English planen “(of a bird) to soar” (compare Middle French planer ); akin to plain ¹

Origin of plane²

First recorded in 1375–1425; Middle English noun plane, plaine, pleine, from Middle French plan(n)e, Old French plaine, plane or directly from Late Latin plāna “plane, adze,” derivative of plānāre “to smooth,” itself derivative of Latin plānus plain ¹; Middle English verb plane(n), plaine, pleine, from Middle French planer or directly from Late Latin plānāre

Origin of plane³

First recorded in 1350–1400; Middle English plane, plaine, from Middle French plane, Old French pleine, plane, from Latin platanus, from Greek plátanos, derivative of platýs “wide, broad, flat” (with reference to the leaves)

Explanation

A plane is a vehicle that flies through the air, but it is also a tool used to make something smooth and flat, a kind of tree or a level surface. As a verb, to plane something is to make it flat and smooth. Don't confuse plane with plain, an adjective that means "simple" or a noun that means "flat land," like the plains of the American Midwest. This can be tricky because plane describes something that is flat and level, or the tool or action that makes something flat and level. If you remember that plain applies only to landforms, the difference will be plain to see — meaning obvious.

Example Sentences

The 10 songs on “The Line of Time and the Plane of Now” — each recorded in only one take — mix folk, soul and jazz, radiating innocence.

From Los Angeles Times • Apr. 3, 2026

Plane maker Airbus on Thursday said it’s having trouble sourcing enough engines as it outlined guidance that disappointed investors.

From MarketWatch • Feb. 19, 2026

Plane maker Airbus aims to deliver a record number of commercial aircraft this year, the company said Thursday, capitalising on "strong demand" and a jump in profit in 2025.

From Barron's • Feb. 19, 2026

Plane deliveries have powered Boeing’s uneven recovery since 2024, when regulators ordered the company to slow production and root out persistent quality-control failures.

From The Wall Street Journal • Jan. 27, 2026

Plane tickets were bought, schedules scheduled, plans laid.

From "Miss Peregrine's Home for Peculiar Children" by Ransom Riggs

Related Words

• airplane
• craft
• jet
• ship