- arcadeA row of arches.
- arcThat part of a circle which a heavenly body appears to pass through as it moves above and below the horizon.
- archAn inverted U shape.
- archerOne who shoots an arrow from a bow or a bolt from a crossbow.
- arsonThe crime of deliberately starting a fire with intent to cause damage.
- arcusA white band of cholesterol that forms at the edge of the cornea
- arbalestA steel crossbow.
- arblastA wooden crossbow with a special drawing mechanism, used to fire bolts, stones, etc.
- arc-Used to form the names of inverse trigonometric functions, and the symbols for these functions.
- archivoltAn ornamental molding or band following the curve on the underside of an arch.
- arciformHaving the form of a bow (weapon)
- arcographAn instrument for drawing a circular arc without using a central point.
- arcosoliumA tomb in an arched recess in a wall.
- arculusA crossvein between the radius and cubitus near the base of the wing in certain insects
- gonarcusAn arched structure that is a principal feature of the male genitalia of some insects.