Other forms: atoms
An atom is the tiniest building block that everything is made of. Split the atom, atoms and molecules, a hydrogen atom.
It is almost entirely empty: the nucleus holds nearly all the mass in a space vastly smaller than the whole. The Greek name means uncuttable, which turned out to be wrong — atoms can be split, and doing so releases the energy behind nuclear power.
1nounatomThe smallest unit of a chemical element.
“A water molecule is made of two hydrogen atoms and one oxygen atom.”
atom is a particle.
Greek atomos means uncuttable, from a-, not, plus temnein, to cut. The name assumed atoms could not be divided.
Middle English
attome
English, today
atom
From Middle English attome. From Middle English attome, from Middle French athome, from Latin atomus (“smallest particle”), from Ancient Greek ἄτομος (“indivisible”), from ἀ- + τέμνω + -ος. Atoms are so named because they were historically thought up as to be the smallest unit of matter, and thus indivisible. a doublet of atomus.
Etymology from Wiktionary, CC BY-SA