I. ˈärk noun
Etymology: Middle English ark, from Anglo-French arc bow, from Latin arcus bow, arch, arc — more at arrow
Date: 14th century
1. : the apparent path described above and below the horizon by a celestial body (as the sun)
2.
a. : something arched or curved
b. : a curved path
the arc of a fly ball
3. : a sustained luminous discharge of electricity across a gap in a circuit or between electrodes ; also : arc lamp
4. : a continuous portion (as of a circle or ellipse) of a curved line
5. : degree measurement on the circumference of a circle — used especially in the phrase of arc
11 minutes 3 seconds of arc
6. : a continuous progression or line of development
a story's dramatic arc
II. intransitive verb
( arced ˈärkt ; arc·ing ˈär-kiŋ)
Date: 1893
1. : to form an electric arc
2. : to follow an arc-shaped course
III. adjective
Etymology: arc sine arc or angle (corresponding to the) sine (of so many degrees)
Date: circa 1949
: inverse 2 — used with the trigonometric functions and hyperbolic functions