My friend Andrew Chamberlain offers up the following as a useful definition of (economic) injustice courtesy of economist Paul Heyne:

It seems to me that our reflections on economic justice would be far more satisfactory if we recognized the connection between justice and the keeping of promises. I have increasingly come to think of justice as basically the fulfillment of legitimate expectations. …Injustice is done, I suggest, when someone’s legitimate expectations are not fulfilled because others broke their promises.

I’ve got to disagree. The minor point is that sometimes an unjust situation itself creates the absence of an expectation. You can probably generate countless examples yourself, but to pick an obvious one: A woman in an illiberal society may have no expectation of being afforded the freedom to earn a living (or to enjoy sexual liberty, or to take part in democratic self-government, etc.). So, at least as a necessary condition for injustice, the violation of a legitimate expectation clearly won’t do, insofar as we want to say that women in such societies are victims of injustice—and I think we do.

The major problem is that “legitimate” is doing all the heavy lifting here. It itself assumes a separate standard of justice, unless we want to index it to some culturally specific notion of legitimacy (what the local rule set leads me to expect), in which case we’re stuck with the problem mentioned above. One might as well say that injustice consists in being denied what one justly expects. It’s true enough, I guess, but empty.