Translation guide
The English word 'arc' has several distinct meanings: a curved shape, a part of a circle, an electric discharge, and a story or character development. This guide covers the most useful Japanese expressions for each meaning.
Describing something that forms a smooth curve, like a rainbow, a bridge, or a trajectory.
The most direct translation for a geometric or physical arc. Used in mathematics, architecture, and descriptions of shapes.
虹は空に美しい弧を描いた。
The rainbow formed a beautiful arc in the sky.
この橋の弧はとても緩やかだ。
The arc of this bridge is very gentle.
Loanword from English 'arch'. Often used for architectural arches or curved structures, but can also mean 'arc' in some contexts.
その門は石のアーチでできている。
The gate is made of a stone arch.
Literally 'bow shape'. Refers to something shaped like a bow, an arc. More descriptive and less technical than 弧.
月が弓形に見える。
The moon looks like a bow shape.
Referring to a segment of a circle's circumference, or a continuous part of a curve.
The standard mathematical term for an arc of a circle. Used in geometry and technical contexts.
円の弧の長さを計算してください。
Please calculate the length of the arc of the circle.
Specifically a circular arc. More precise than 弧 alone.
A luminous discharge of electricity through a gas, like in welding or lightning.
Loanword from English 'arc', used in technical contexts like arc welding or arc lamps.
アーク溶接は金属を接合するのに使われる。
Arc welding is used to join metals.
A more formal or older term for electric arc. Rarely used in everyday language.
電弧が発生した。
An electric arc occurred.
A continuous storyline or the progression of a character over time in a narrative.
Loanword used in media and literature to refer to a story arc. Common in discussions of anime, manga, and games.
このアニメの次のアークはとても面白い。
The next arc of this anime is very interesting.
彼のキャラクターアークは感動的だった。
His character arc was moving.
Means 'story development' or 'plot progression'. A more native Japanese way to refer to the arc of a story.
この物語の展開は予想外だった。
The arc of this story was unexpected.
Direct loan of 'story arc'. Used in the same way as アーク but more explicit.
このストーリーアークは長すぎる。
This story arc is too long.
弧 (こ) is for physical or geometric arcs. アーク is for electric arcs and story arcs. Using 弧 for a story arc would be unnatural.
このアニメの弧は面白い。
The arc of this anime is interesting. (incorrect)
This curve is part of a circular arc.