expert vs reckoner

Other hyponyms of expert include ace, adept, champion, genius, hotshot, maven, mavin, sensation, star, superstar, virtuoso, whiz, whizz, wiz, wizard, agronomist, all-rounder, all arounder, analyst, analyst, anatomist, antiquarian, antiquary, archaist, arbiter, supreme authority, archer, bowman, authority, black belt, cabalist, kabbalist, calculator, computer, estimator, figurer, climatologist, computer expert, computer guru, cosmetologist, efficiency engineer, efficiency expert, exegete, genealogist, geographer, horticulturist, plantsman, investigator, jurist, legal expert, lapidarist, lapidary, logician, logistician, mnemonist, mythologist, nerd, commentator, observer, out-and-outer, parliamentarian, past master, prosthetist, pteridologist, guide, pathfinder, scout, shark, shooter, shot, specialiser, specialist, specializer, talent, technician, technocrat, healer, therapist, old-timer, old hand, old stager, oldtimer, stager, veteran, warhorse.