How to say "arc" in Japanese

Choosing the right word

アークCommon
nounThe borrowed word, used chiefly in technical and scientific contexts, above all for an electric arc; it can also mean a story arc in fiction. Not the everyday word for a curved line.
弧こCommon
nounThe general word for an arc as a curved line: any portion of a curve, in geometry or in describing shapes. Neutral and widely usable when you simply mean a curved, arc-shaped line.
要素ようそＣとＤは弧この生成せいせいには無関係むかんけいなので排除はいじょすることができる。↗
We can eliminate C and D since they are irrelevant to the generation of the arcs.
円弧えんこCommon
nounSpecifically an arc of a circle: a part of its circumference. The precise term in geometry and mathematics when the curve in question is circular rather than just any curved line.

Use 「アーク」 for technical senses such as the electric arc, 弧 for an arc as a general curved line, and 円弧 when the arc is specifically part of a circle.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

Japanese equivalents

Say it right, write it right