For. The. Love. Of. Christ.
Look, people, words mean things, and, Humpty Dumpty notwithstanding, they mainly mean what they are understood to mean by the people who create and employ them. Wittgenstein also notwithstanding, we mostly don't have trouble agreeing about most of the things that fall into most of the categories we choose to assign to the phenomena we observe.
Somebody posted a link to a very clear definition of "concentration camp" as the term is employed by people who spend their whole damned lives talking about, thinking about, and teaching about things like concentration camps. Nonetheless, there are people on this site who continue to insist on disputing the definition. Well, nobody gives a flying fuck if you think "concentration camp" means "A place where people are rounded up and murdered," or in fact, means anything other than what it does mean, which is this: A place where civilians are collected and kept, normally without evidence or even suspicion of a crime, nevermind an accusation, so that they can be controlled. The "concentration" being referred to has nothing to do with whether they are overcrowded or underfed or gassed or raped or anything else -- it just means, they are put together, in one place, so that whatever power put them there can keep an eye on them.
The original concentration camps were a colonial measure for rounding up a dispersed population so that they could easily be policed and kept separate from insurgents. That's the "concentration" in question: Rather than having them scattered around the landscape on farmsteads and in rural villages, they were all in one place, gathered up and put behind fences, where they couldn't lend aid to insurgents -- couldn't feed them, or hide them, or give them information. That was the whole deal.
There is simply no disputing that the internment camps in which the US placed people of Japanese ethnicity were concentration camps. They were practically definitional concentration camps. Anybody arguing that these internment camps were not concentration camps might as well be arguing that the buildings in which NHL teams play their games are not "arenas". Or that American high schools aren't "schools". Or that Kroger's venues are not "grocery stores". You don't get the choice. You don't get to argue. You don't get to have a contrary opinion on this, anymore than you get to have a contrary opinion on whether grass is a plant or bats are mammals. It. Is. A. Fact. Live with it.
Your own (or anybody else's) emotional response to the most horrifying exemplars of concentration camps does not somehow overrule the perfectly functional definition of "concentration camp", which subsumes the Nazi death camps and a lot of other appalling instances as well. Concentration camps existed before the Nazis. They have existed since the fall of the Nazis. They are likely to exist for as long as our civilization teeters along. Himmler and Speer didn't invent concentration camps, and their "innovations" didn't change the definition of the phenomenon.
Note finally that people who know what the fuck they're talking about generally don't include PoW camps as concentration camps -- though in some instances they might be thought to meet the definition. Similarly, prison camps (such as prison farms) where people have been sent to serve out sentences under much different conditions than, say Leavenworth, are usually not considered concentration camps. Pay no attention to Solzhenitsyn. He was a bigot, a religious fanatic, and an idiot. (That said, in casual usage, some people might extend the definition of "concentration camp" to include those categories, particularly under certain circumstances -- but that is (or should be) casual usage, and when done it degrades and blurs the more precise and accurate definition, to the overall detriment of our language.)
Is Gaza a concentration camp? Yes, we can debate that question. It sure fucking looks like one. The fact that people come and go does not violate the definition. Internees in concentration camps often come and go. How else are they to earn their keep? Even in Nazi Germany, inmates came and went from the camps -- marched off to work in factories as slave labor, then marched back to their fenced-in barracks. Arbeit Macht Fucking Frei, and all that.
I can't believe we even have to argue about this.