Full Idea
The word 'unjust' is considered to describe both one who breaks the law and one who takes advantage of another, i.e. acts unfairly.
Gist of Idea
The word 'unjust' describes law-breaking and exploitation
Source
Aristotle (Nicomachean Ethics [c.334 BCE], 1129a32)
Book Reference
Aristotle: 'Ethics (Nicomachean)', ed/tr. ThomsonJ A K/TredennickH [Penguin 1976], p.172
A Reaction
Roughly, injustice is bad dealings with fellow citizens. We have 'distributive justice', and justice in keeping contracts. Our central meaning, of giving each citizen what they deserve, doesn't seem to be here.