Other forms: arcs, arcing
An arc is a curve — strictly, a piece taken out of the edge of a circle. The path a thrown ball draws through the air, the clean sweep a wiper clears on a wet windscreen, the line a compass leaves on the page.
In geometry an arc is measured in degrees and belongs to a named circle. In everyday use it is any curved path: the ball rose in a lazy arc, water arced out of the hose. Electricians and welders mean something else again — an arc is the bright jump of current across a gap, which is where arc welding gets its name. And in books and television a story arc or a character arc is the shape a person's change takes across the whole thing. One warning: an arc is not an ark. Noah's boat is a different word with a different family.
1nounarcA curved line, especially part of the edge of a circle.
“The compass drew a neat arc across the page.”
synonyms: curve
2nounairA curved path through the air.
“The ball rose in a high arc over the defenders.”
3verbmoveTo move along a curved path.
“Water arced out of the hose and landed on the path.”
4nounstreamA stream of electricity jumping across a gap.
“A blue arc jumped between the two terminals.”
5nounshapeThe shape of a character's or a story's development over time.
“Her arc takes up the whole second season.”
Too few real examples of this word to estimate which sense is commonest.
arc is a curve.
Latin arcus meant a bow, an arc, an arch, and behind it stands Proto-Indo-European *h₂erkʷos, 'bow, arrow'. English took it through Old French arc. Arch and arrow grew from the same root, so an arc is, at heart, the shape a drawn bow makes.
Middle English
ark
English, today
arc
From Middle English ark. Middle English ark, from Old French arc, from Latin arcus (“a bow, arc, arch”), ultimately from Proto-Indo-European h₂erkʷos (“bow, arrow”). a doublet of arch and arco and arrow.
Etymology from Wiktionary, CC BY-SA