四角形（しかくけい、shikakukei）
- quadrilateral

The Japanese word 四角形 しかくけい refers to a "quadrilateral" or a "four-sided shape" in geometry. It specifically describes a two-dimensional figure that is enclosed by four straight line segments (sides). The word emphasizes the presence of four corners (angles) and four sides. The shape can be various forms, like squares, rectangles, rhombuses, parallelograms, trapezoids, or even irregular shapes with four sides.

Here are some examples: ⚫︎このテーブルは四角形です。 Translation: This table is a quadrilateral (or has a rectangular shape). ⚫︎四角形の面積を計算してください。 Translation: Please calculate the area of the quadrilateral. ⚫︎四角形の内角の和は360度です。 Translation: The sum of the interior angles of a quadrilateral is 360 degrees.

You use 四角形 in conversations related to geometry, shapes, or design. It's appropriate when describing or referring to objects with four sides. You could use it when talking about construction, art, or everyday objects like tables, windows, or signs. It is a common term when studying math in school or discussing shapes and dimensions.

四角形 is typically written in kanji 四角形. The reading in hiragana is しかくけい. There are no common variations in the okurigana.

There aren't many direct synonyms for 四角形, as it is a specific geometric term. However, you could use more descriptive terms depending on the type of quadrilateral: ⚫︎長方形 (ちょうほうけい) - rectangle ⚫︎正方形 (せいほうけい) - square ⚫︎ひし形 (ひしがた) - rhombus You might also use a general term like 図形 (ずけい) - figure or shape, but it's not a direct synonym.

There is no direct antonym for 四角形, because it refers to a specific type of shape. However, you could consider terms for shapes with a different number of sides. For example: ⚫︎三角形 (さんかくけい) - triangle (three sides) ⚫︎五角形 (ごかくけい) - pentagon (five sides) ⚫︎円 (えん) - circle (no sides, curved)

この窓は四角形のガラスでできています。 ・Translation: This window is made of quadrilateral (rectangular) glass. ・Explanation: This sentence uses 四角形 to describe the shape of the window's glass.

子供たちは四角形のブロックで家を作った。 ・Translation: The children built a house with quadrilateral (square or rectangular) blocks. ・Explanation: This example explains how kids were using the 四角形-shaped blocks for building.

The word 四角形 is a compound word. ⚫︎四 (し) - "shi" means "four". ⚫︎角 (かく) - "kaku" means "corner" or "angle." ⚫︎形 (けい) - "kei" means "shape" or "form." So, literally, 四角形 is "four-corner shape," reflecting its fundamental characteristics.