noun
atom
A-tuhm
noun
1
The smallest unit of a chemical element that retains its properties, made up of a nucleus and surrounding electrons.
"Every atom of oxygen has eight protons."
"Splitting the atom released enormous amounts of energy."
2
A tiny or minimal amount of something.
"There isn't an atom of truth in that rumor."
How to Use Atom
Learner’s notesIn plain EnglishThe basic building block of matter — or, informally, the tiniest possible amount of something.
Common pairings
split the atom
an atom of truth
Word Forms
atoms plural
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Every _____ of oxygen has eight protons.
Etymology
From Latin atomus, from Greek atomos ("indivisible"), from a- ("not") + temno ("to cut"). Ancient philosophers imagined atoms as the smallest possible pieces of matter, though we now know atoms themselves are divisible.