三角錐（さんかくすい、sankakusui）
- triangular pyramid

The Japanese word 三角錐 (さんかくすい, *sankakusui*) refers to a "triangular pyramid" in English. It is a three-dimensional geometric shape. ⚫︎ A triangular pyramid has a base that is a triangle. ⚫︎ From each vertex (corner) of the triangular base, lines extend upward to meet at a single point called the apex (or vertex). ⚫︎ The other three faces are also triangles.

⚫︎ 三角錐の体積を計算してください。 Translation: Please calculate the volume of the triangular pyramid. ⚫︎ この建物は三角錐の形をしています。 Translation: This building is shaped like a triangular pyramid. ⚫︎ 三角錐の展開図を描く。 Translation: Draw the net of a triangular pyramid.

三角錐 is used in mathematical contexts, such as geometry lessons, architectural discussions, or any situation where you are discussing the shape or properties of a triangular pyramid. You can use it when describing the form, volume, or other characteristics of these shapes.

⚫︎ 三角錐 is typically written in kanji and hiragana: ⚫︎ Kanji: 三角錐 ⚫︎ Hiragana: さんかくすい ⚫︎ The word is not usually written in katakana unless for emphasis or in a very specific context, such as referring to a model name. ⚫︎ There are no significant variations in the okurigana (the suffix hiragana) of this word. The spelling is fixed.

There are no perfect synonyms for 三角錐 in common use. However, you could use more descriptive phrases: ⚫︎ "Triangle pyramid" (in English) could be directly translated. ⚫︎ "Pyramid with a triangular base" (if you want to be more descriptive).

There isn't a direct antonym for 三角錐. Antonyms would depend on what aspect of the shape you are contrasting. Some examples: ⚫︎ You could contrast the base shape: "square pyramid" or 四角錐 (*yonkakusui*) (a pyramid with a square base). ⚫︎ You could contrast the three-dimensional aspect with a two-dimensional shape like a triangle.

数学の授業で、三角錐の体積の公式を学びました。 ・Translation: In math class, we learned the formula for the volume of a triangular pyramid. ・Explanation: This sentence uses 三角錐 in a general educational context.

その彫刻は、完璧な三角錐の形をしていました。 ・Translation: That sculpture had a perfect triangular pyramid shape. ・Explanation: This sentence uses 三角錐 to describe the form of an object.

The word 三角錐 (さんかくすい) is a compound word. It is formed by combining: ⚫︎ 三角 (*sankaku*) meaning "triangle" (literally "three corners"). ⚫︎ 錐 (*sui*) meaning "pyramid" or "cone". Therefore, the word literally means "triangle pyramid" or "triangular cone".