六角形（ろっかくけい、roっkakukei）
- hexagon

The Japanese word 六角形 (rokkakkei) means "hexagon" in English. A hexagon is a two-dimensional shape with six sides and six angles. It is a polygon, meaning it is a closed shape with straight sides. The internal angles of a hexagon always add up to 720 degrees. Both regular and irregular hexagons exist. A regular hexagon has all sides and all angles equal.

⚫︎そのハニカム構造は六角形の形をしている。 Translation: That honeycomb structure has a hexagonal shape. ⚫︎六角形のテーブルは部屋の真ん中に置かれた。 Translation: The hexagonal table was placed in the middle of the room.

You would use 六角形 when you are talking about or describing a hexagon, or something that is hexagonally shaped. It is a relatively common word, used in geometry, architecture, design, and other fields. It can be used in both formal and informal contexts.

⚫︎The word is typically written using the kanji 六 (roku - six), 角 (kaku - corner, angle), and 形 (kei - shape). ⚫︎Hiragana: ろっかくけい ⚫︎Katakana: While not commonly used, it could be written as ロッカッケイ for emphasis or in specialized contexts like technical diagrams. ⚫︎There is no variation in the okurigana for this word.

There are no direct synonyms for 六角形 in Japanese, as it is a specific geometrical term. However, you might use more descriptive phrases to convey the idea if necessary, such as: ⚫︎六つの辺を持つ図形 (Muttsu no hen o motsu zukei) - "A figure with six sides".

There aren't specific antonyms in the same way as words like "hot" and "cold." However, you could consider the opposite to be shapes that do not have six sides, for example: ⚫︎三角形 (sankakkei) - Triangle ⚫︎四角形 (shikakkei) - Quadrilateral

数学の授業で六角形の面積の計算方法を習った。 ・Translation: In math class, I learned how to calculate the area of a hexagon. ・Explanation: This sentence describes the context of learning about the geometric concept of a hexagon.

このデザインは、六角形を組み合わせたパターンを使っています。 ・Translation: This design uses a pattern that combines hexagons. ・Explanation: This sentence discusses the application of hexagons in design.

The word 六角形 is a compound word: ⚫︎六 (roku) means "six." ⚫︎角 (kaku) means "corner" or "angle." ⚫︎形 (kei) means "shape" or "form." Therefore, 六角形 literally translates to "six-cornered shape," accurately describing the geometric figure. The word was likely adopted into Japanese from Chinese or directly from the Western mathematical concepts.