polyhedron
多面体
解説 Definition
平らな多角形の面で囲まれた三次元の立体図形。幾何学において、頂点、辺、面の関係を研究する対象です。
A polyhedron is a solid shape with many flat faces, straight edges, and corners. The word is used in mathematics and geometry for 3D forms such as cubes and pyramids.
覚え方のコツ Memory Tip
まず poly- は polygon, polyglot などでも出る「多い」。この語の核は後半の -hedron で、tetrahedron（四面体）, octahedron（八面体）にも共通し、「面をもつ立体」の仲間だと覚えると定着しやすいです。polygon が 2D の「多角形」なのに対し、polyhedron は 3D の「多面体」。point や line ではなく flat faces に注目する語で、幾何で『面・辺・頂点をもつ立体』を見たらこれを思い出すと結び付きます。
`Poly-` means many, as in `polygon` or `polyglot`. The important part is `-hedron`, which you also see in `tetrahedron` and `octahedron`, so you can group them as shape words. A `polygon` is flat, but a `polyhedron` is the 3D version with many faces.
例文
A polyhedron is a three-dimensional solid bounded by flat polygonal faces.
多面体は平らな多角形の面で囲まれた三次元の立体です。
A cube is a simple example of a polyhedron with six square faces.
立方体は6つの正方形の面を持つ多面体の簡単な例です。
The properties of polyhedrons are studied extensively in geometry.
多面体の特性は幾何学で広く研究されています。
polyhedron の類義語・関連語
polyhedron の語源・成り立ち Etymology
ギリシャ語 polyedron に由来し、poly-「多くの」＋ hedra「座・面」から成る。hedra は「座る場所」から幾何学の「面」へ意味が広がったので、polyhedron は文字どおり「面がたくさんあるもの」。関連語は tetrahedron, octahedron。
Polyhedron comes from Greek polyedron. It is made from poly- meaning "many" and hedra meaning "seat" or later "surface" or "face." As the second part widened in meaning from a place to sit to a geometric face, the whole word came to mean something with many faces. It is closely related to tetrahedron and octahedron.
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