The definition of rent is pretty straightforward. Did you earn it in exchange for a labor or service? That's wages. Did you earn it by employing, deploying, lending, or multiplying capital? That's called interest. Did you earn it by any means besides the above, especially by exploiting a monopoly or special privilege granted by government? That's rent, and it's almost non-existent in free markets, but is the dominant cause of stagnation, suffering, and inequality in "advanced" economies ("advanced" in quotes because historically entire classes existed by collecting rent; this was supposed to have been eliminated by a government where all were equal under the law and without special privilege, under what Thomas Jefferson called "pure republicanism". But he failed to appreciate, as Henry George later did, that there cannot be both equality under the law and capitalization of land. Jefferson didn't live to see industrialization, or he would have doubled down on the land politics he already held, which were essentially that of the French Physiocrats. "It is not too soon to provide by every possible means that as few as possible shall be without a little portion of land. The small landholders are the most precious part of a state…."--Thomas Jefferson . Unfortunately it was in fact slightly too soon, because America was still a frontier then, and rent more or less irrelevant, as rent cannot be imposed on a good as long as more of that good (namely land) can be got at the margins, per Ricardo's law of Rent. Many people think of land politics as being an agrarian topic, but paradoxically it's urbanization and industrialization that catapults rents).
