arch-(word root)1. principalExamples: archenemy2. prototypicalExamples: archetype3. chief, leader, rulerExamples: monarch, matriarchAbused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embreearch- 1pref.1. Chief; highest; most important: archenemy.2. Extreme or most characteristic of its kind: archconservative.[Middle English arche-, from Old English ærce- and from Old French arche-, both from Latin archi-, from Greek arkhi-, archi-.]arch- 2pref. Variant of archi-.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.arch- or archi-combining form1. chief; principal; of highest rank: archangel; archbishop; archduke. 2. eminent above all others of the same kind; extreme: archenemy; archfiend; archfool. [ultimately from Greek arkhi-, from arkhein to rule]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014arch1 (?rt?) n. 1. a curved construction spanning an opening and usu. supporting weight from above or the sides. 2. a doorway or gateway having a curved head; archway. 3. any overhead curvature resembling an arch. 4. something bowed or curved: the arch of the foot. v.t. 5. to cover or span with an arch. 6. to form into an arch: a cat arching its back. v.i. 7. to form an arch: elms arching over the road. [1250?1300;