{ 1 } - the correct ordering of the parts of the soul, whereby the rational part guides the spirited part, and both together guide the appetites.
{ 2 } - upsetting distributions of pleasure or happiness that don't accord with merit.
{ 3 } - treating others fairly.
{ 4 } - the equal liberty and the difference principle.

There are different areas of justice. For example, distributive justice deals with the distribution by merit of wealth and honors; and corrective justice deals with punishments.

What is just is determined partly by nature and partly by convention: while it's by nature just that criminals be punished, the civil law determines which punishment goes with which crime.