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1 a person with a high level of knowledge or skill in a field took a few lessons with a tennis ace to improve his backhand Synonyms expert, adept, artist, authority, cognoscente, connoisseur, crackerjack (also crackajack), dab [chiefly British], dab hand [chiefly British], fiend, geek, guru, hand, hotshot, maestro, master, maven (also mavin), meister, past master, proficient, scholar, shark, sharp, virtuoso, whiz, wizardRelated Words pro, professional; consultant, hired gun, specialist; addict, aficionado (also afficionado), buff, devotee, enthusiast, fan; craftsman, journeyman; all-rounder [British], jack-of-all-trades, Renaissance man; mistressNear Antonyms apprentice, beginner, neophyte, novice; dabbler, dilettante; layman, nonprofessionalAntonyms amateur, inexpert, nonexpert

2 a very small amount not an ace of truth in what she said Synonyms particle, bit, crumb, dab, dram, driblet, glimmer, hint, lick, little, mite, nip, ounce, peanuts, ray, scintilla, scruple, shade, shadow, shred, skosh, smack, smell, smidgen (also smidgeon or smidgin or smidge), snap, soupçon, spark, spatter, speck, splash, spot, sprinkling, strain, streak, suspicion, tad, touch, traceRelated Words hoot, iota, jot, minim, minimum, modicum, semblance, syllable, tittle, vestige, whit; atom, dot, fleck, flyspeck, grain, granule, molecule, morsel, mote, nubbin, patch, scrap; dash, drop, pinch; part, portion, section; bite, nibble, taste; handful, scattering, smatter, smattering; dose, shot; chip, flake, fragment, shard, shiver, sliver, smithereens, splinter; shred, tatter; clipping, paring, shavingNear Antonyms abundance, barrel, boatload, bucket, bundle, bushel, deal, fistful, gobs, heaps, lashings (also lashins) [chiefly British], loads, lot, mass, mess, mountain, much, oodles, passel, peck, pile, plenty, potful, profusion, quantity, raft, reams, scads, stack, wad, wealth; volume; bonanza, embarrassment, excess, overabundance, overage, overflow, overkill, overmuch, oversupply, superabundance, superfluity, surfeit, surplus; chunk, hunk, lump, slab

3 a very small distance or degree came within an ace of being chosen for the part Synonyms hair, hairbreadth (or hairsbreadth), hairline, hop, skip, and jump, inch, neck, shouting distance, step, stone's throwRelated Words bit, crumb, dab, iota, jot, minim, mite, particle, smidgen (also smidgeon or smidgin or smidge), trace, trifleNear Antonyms infinity, light-yearAntonyms country mile, long haul, mile