Edit: Turned out to be a rather long reply with some background and descriptions of the differences and historical references. Outlines theoretical difference between socialism and communism as outlined by Marx, and then gets into why it's hard to nail down terminology in this sphere.

> "/s" is often used to connote sarcasm, in written text

Gotcha - missed the sarcasm that time.

> Recently, American politics has some groups label any regulation or public service as "socialism"; eg, "the FDA is socialism!"

Well, the FDA sucks in that it turns a huge blind eye to some horrible stuff while regulating some real petty, unnecessary stuff, and adds a lot of cost. For instance, fiber isn't considered an essential nutrient, so foods stripped of all fiber (most fast food) is perfectly legal, but other stuff is banned/controlled rather capriciously. But no, it's not socialism, just generic idiot bureaucracy.

> I've usually heard "communism" used to describe State-owned industry, whereas "socialism" is worker-owned.

Marx defined communism as a classless, rulerless society in perfect peace and harmony and infinite production and happiness and unity for everyone. However, he said the world would have to get through violent revolution. So it would be appropriate to say that socialism is government ownership of means of production, and workers control the government in some form or fashion.

> For example, profit-sharing, privately-owned co-ops, or credit unions would be socialism, under this definition

Nah, that's good ol' fashioned free enterprise right there, or capitalism if you prefer the term. I'm against socialism/communism because it doesn't work very well, but I'm very supportive of co-ops, worker ownership in a business, voluntary community-owned and sponsored projects, etc. None of that is socialism/communism, which includes threats of force/imprisonment/violence for doing subversive free market activities.

> North Korea would be communist but certainly not socialist. Is this definition outmoded or incorrect? I'd like to have a more accurate vocabulary for discussing these sort of things.

It's tricky to get a correct vocabulary, because people like to continually rebrand their political positions to sound more favorable. The Soviet countries called themselves Communist, but clearly didn't fit Marx's definition of ideal communism. That said, Marx's definition of ideal communism is literally impossible - people will always rank themselves, and when you take away the ability for people to rank themselves based on a particular criteria, they just pick something else. And often they pick something worse - party loyalty, military accomplishment, or academic accomplishment (except that academia is now controlled by the government, so academic work outside of the natural sciences all devolves into propaganda).

To give you an idea of the shifting lines and why it's hard to get a good vocabulary - Nazi Germany was clearly heavily socialist. "Nazi" is short for "Nazionalsocialiste". Hitler's party was the National Socialist German Worker's Party.

They actually did directly control a lot of industry. If you read some of Table Talk, which are basically minute-by-minute summaries of Nazi cabinet meetings recorded for preservation by Nazis, Hitler was constantly talking about planning the farming in Ukraine, or the chemicals production in Bavaria, or changing how the universities run in Vienna, or making cruises or automobiles more accessible to the people.

Clearly, clearly, clearly socialism under Marx's definition. They hated the Russians, but saying Hitler hated Communism isn't quite accurate - he constantly talked about how "Bolshevism" was a huge problem, that was the Russian implementation. He didn't knock socialism/communism-itself very often.

But what do sociologists typically label Nazi Germany these days? "Corporatist". Hmm, what's that? Turns out "corporatist" is socialism where the the company is fully owned by the government, but has some very loose semi-autonomous management. It's basically just normal socialism. Yet it's called "corporatism", which anyone who isn't a sociologist would associate with corporations/capitalism/etc. It's not. The NSDAP (Nazionalsocialiste Deutsche Arbetitet Partei - The National Socialist German Worker's Party - shorthand, Nazis) were clearly a heavily socialist government.

But people who generally favor state-ownership don't want that association, so they call it "corporatism", which is just unnecessarily misleading and false. For all the things socialism does poorly, it actually does perform as well as capitalism at making war. The reason is that you can have the leader order a bunch of separate industries to work together - you get all the country's brightest people working on war under socialism. Amazingly, the USA was able to convince its best and brightest to largely volunteer for the war effort, but this is a rare thing. Under socialism, it's usually a lot easier to make war than worrying about getting industry to voluntarily participate. That's about the only thing socialism does better though - it starts to move too slowly and stagnate when there's more than one goal for the government to pay attention to, or the goal isn't extremely straightforward. One of the biggest things that breeds laziness and complacency is lack of competition; that's solved during wartime by the enemy. So socialism does okay at war, and pretty poorly at fulfilling diverse and changing wants and needs.