standard definition $n$-torsion-free

Question

From the book Dummit and Foote, there written about torsion element, and it is prevailing in Module section. But what is the definition of $n$-torsion-free? particularly, $n$-torsion-free near-ring? From the paper I read, a near-ring $N$ is said to be $n$-torsion-free, if $nr=0$ implies $r=0$ for all $r$ in $N$. While I search more about $n$-torsion-free, I found a Wikipedia article on the torsion-free group, and it is similar. Is the definition of $n$-torsion free near ring derived from the notion of a torsion-free group? or it is likely in Dummit and Foote? Is there any book that stated briefly the standard definition of the torsion-free group or torsion-free near ring that can be cited?