plane figure
- noun
- /pleɪn ˈfɪɡər/
- Specialized
:
figura plana
- The artist used a circle, a basic plane figure, as the focal point of her painting.
Examples
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For instance, one can define a rectangle as a four-sided plane figure whose angles are all 90 degrees.
Academic text (2015) -
A rectangle is a plane figure with four sides and four right angles.
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In geometry class, we learned that a triangle is a simple plane figure made up of three straight sides.
Synonyms
A flat shape like a square or circle with length and width but no depth
How Complex
Surface Forms
Morphology
The meaning 'a two-dimensional geometric shape' is directly and compositionally derived from 'plane' (flat, two-dimensional surface) + 'figure' (shape), so knowing the constituents makes the MWE predictable. This is a standard geometric term with transparent semantics and cross-linguistic parallels, so a B1 learner who knows both words would readily understand it.
Etymology
Plane figure comes from the idea of a flat surface and a shape on it: plane means a flat area and figure means a shape. So a plane figure is a 'flat' shape that lies on one surface, like a circle or square.