What is Private Law?

Legal Definition
Private law is that part of a civil law legal system which is part of the jus commune that involves relationships between individuals, such as the law of contracts or torts (as it is called in the common law), and the law of obligations (as it is called in civil legal systems). It is to be distinguished from public law, which deals with relationships between both natural and artificial persons (i.e., organizations) and the state, including regulatory statutes, penal law and other law that affects the public order. In general terms, private law involves interactions between private citizens, whereas public law involves interrelations between the state and the general population.
-- Wikipedia
Legal Definition
An act of the legislature which relates to some private matters, which do not concern the public at large.
-- Bouviers Law Dictionary
Legal Definition
As used in contradistinction to public law, the term means all that part of the law which is administered between citizen and citizen or which ls concerned with the definition, regulation, and enforcement of rights in cases where both the person in whom the right inheres and the person upon whom the obligation is incident are private individuals. See Public Law.
-- Black's Law Dictionary