atomic

(physics, chemistry) Of or relating to atoms; composed of atoms; monatomic.

Employing or relating to nuclear energy or processes.

Infinitesimally small.

(programming, of a commit in a VCS) Containing a single change, as opposed to involving numerous unrelated changes.

(logic, of a proposition) Lacking logical operators; unable to be made simpler in logical form.

(computing, of an operation) Guaranteed to complete either fully or not at all while waiting in a pause, and running synchronously when called by multiple asynchronous threads.