Private law is that part of a legal system that governs interactions between individual persons.
In general terms, private law involves interactions between private individuals, whereas public law involves interrelations between the state and the general population.
[2] "huius studdii duæ sunt positiones: publicum et privatum.
Publicum ius est, quod statum rei Romanæ spectat, privatum, quod ad singulorum utilitatem; sunt enim quædam publice utila, quædam privatim".
"Considered as inhabitants of so great a planet, which necessarily contains a variety of nations, they have laws relating to their mutual intercourse, which is what we call the law of nations.