弧（こ、ko）
- arc

The Japanese word 弧 (読み方：こ, *ko*) primarily refers to a curve, specifically a segment of a circle or an arc. It's used in various contexts, from describing shapes in geometry to figurative expressions. Think of it as a part of a circle's circumference. The word can also carry a sense of curvature in general, not just in a mathematical sense.

⚫︎円弧 Translation: Arc of a circle ⚫︎弓弧の形 Translation: The shape of a bow (referring to its curved form) ⚫︎弧を描く Translation: To draw an arc/curve

⚫︎You'd use 弧 when discussing or describing curved shapes. ⚫︎It's common in geometry, architecture, or any field involving curved lines. ⚫︎You can also use it metaphorically to describe a curved path or a gradual process. ⚫︎While it can appear in everyday conversation, it's more frequent in technical or descriptive contexts.

⚫︎The word is most commonly written in kanji: 弧. ⚫︎The hiragana reading is こ (*ko*). ⚫︎There are no variations in okurigana for the kanji 弧. ⚫︎It isn't typically written in katakana.

⚫︎カーブ (*kaabu*): Curve (borrowed word, more general) ⚫︎曲線 (*kyokusen*): Curve (formal, in mathematics or technical contexts) ⚫︎アーチ (*aachi*): Arch ⚫︎弓形 (*kyūkei*): Bow-shaped

⚫︎直線 (*chokusen*): Straight line

数学の授業で、弧の長さを計算しました。 ・Translation: In math class, we calculated the length of the arc. ・Explanation: This sentence uses 弧 in a mathematical context, referring to a segment of a circle's circumference.

夕焼けが空に美しい弧を描いていた。 ・Translation: The sunset was drawing a beautiful arc in the sky. ・Explanation: This sentence uses 弧 in a more descriptive, figurative way to describe the curved shape of the sunset.

The kanji 弧 is composed of the following: ㇕ which means "bow" and 古 which means "old" or "ancient". It’s likely related to the shape of a bow (a curved shape) and therefore represents "an arc" or "curve" which derives from a circle.