In a particular branch of logic, certain concepts are at such a basic level of simplicity they can not be broken down into anything simpler.
Those concepts are called atoms or described as atomic.
Different branches of logic admit different atoms.
Also defined as
The word atom comes from the Greek ἄτομον, meaning unbreakable or indecomposable.
It is pronounced with a short a, as at-tom, as opposed to ay-tom.
- 2000: Michael R.A. Huth and Mark D. Ryan: Logic in Computer Science: Modelling and reasoning about systems ... (previous) ... (next): $\S 1.1$: Declarative sentences