円弧|えんこenko[1]atamadaka (head-high)

1. nounarc

• Synonym弧こNeutralAlso an arc, but slightly broader than 「円弧」: it can cover similar curves such as part of a parabola, as in 「弧を描く」.
• SynonymアークNeutralA loanword that usually means an electric arc, as in 「アーク溶接」, or arc length in math; for everyday geometric arcs 「円弧」 or 「弧」 is the usual choice.
• Synonym弧線こせんWrittenMeans the same as 「円弧」—a curve forming part of a circle—but is written/formal prose and little used; in everyday speech say 「弧」.
• Antonym直線ちょくせんNeutralA straight line, common in everyday use; in terms of line shape it is the opposite of the curved 「円弧」.

For a geometric arc, say 「円弧」 or the shorter 「弧」, as in 「弧を描く」. Use 「アーク」 for electric arcs such as welding, and 「直線」 for the straight line that contrasts with a curved 「円弧」.

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

1. 円周えんしゅうを切り取きりとった一部分いちぶぶん。