physics and chemistry The smallest component of an element having the chemical properties of the element.

Roget 180a: inextension^†, nonextension^†, point; dot; atom etc. (smallness) 32.   

Roget 193: littleness etc. adj.; smallness etc. (of quantity) 32; exiguity, inextension^†; parvitude^†, parvity^†; duodecimo^†; Elzevir edition, epitome, microcosm; rudiment; vanishing point; thinness etc. 203.    dwarf, pygmy, pigmy^†, Liliputian, chit, pigwidgeon^†, urchin, elf; atomy^†, dandiprat^†; doll, puppet; Tom Thumb, Hop-o'-my-thumb^†; manikin, mannikin; homunculus, dapperling^†, cock-sparrow.    animalcule, monad, mite, insect, emmet^†, fly, midge, gnat, shrimp, minnow, worm, maggot, entozoon^†; bacteria; infusoria^†; microzoa [Micro.]; phytozoaria^†; microbe; grub; tit, tomtit, runt, mouse, small fry; millet seed, mustard seed; barleycorn; pebble, grain of sand; molehill, button, bubble.    point; atom etc. (small quantity) 32; fragment etc. (small part) 51; powder etc. 330; point of a pin, mathematical point; minutiae etc. (unimportance) 643.    micrometer; vernier; scale.    microphotography, photomicrography, micrography^†; photomicrograph, microphotograph; microscopy; microscope (optical instruments) 445.    ... show more

Dutch: atoom
Polish: atom

nontechnical usage A tiny piece of anything.

synonyms: corpuscle, molecule, mote, particle, speck.

Roget 32: smallness etc. adj.; littleness etc. (small size) 193; tenuity; paucity; fewness etc. (small number) 103; meanness, insignificance (unimportance) 643; mediocrity, moderation.    small quantity, modicum, trace, hint, minimum; vanishing point; material point, atom, particle, molecule, corpuscle, point, speck, dot, mote, jot, iota, ace; minutiae, details; look, thought, idea, soupcon, dab, dight^†, whit, tittle, shade, shadow; spark, scintilla, gleam; touch, cast; grain, scruple, granule, globule, minim, sup, sip, sop, spice, drop, droplet, sprinkling, dash, morceau^†, screed, smack, tinge, tincture; inch, patch, scantling, tatter, cantlet^†, flitter, gobbet^†, mite, bit, morsel, crumb, seed, fritter, shive^†; snip, snippet; snick^†, snack, snatch, slip, scrag^†; chip, chipping; shiver, sliver, driblet, clipping, paring, shaving, hair.    nutshell; thimbleful, spoonful, handful, capful, mouthful; fragment; fraction etc. (part) 51; drop in the ocean.    animalcule etc. 193.    trifle etc. (unimportant thing) 643; mere nothing, next to nothing; hardly anything; just enough to swear by; the shadow of a shade.    finiteness, finite quantity.    ... show more

Dutch: splinter, stofdeeltje, vuiltje, partikel, deeltje
Polish: atom