Is it purely semantics?
The only thing I can tell is that “cocoa” may have less milk fat.
For that matter (I haven’t had time to research it): What’s the difference between apple cider and apple juice?
Cecil has already addressed your last question. What’s the difference between apple juice and apple cider?
Wiki says they are one-in-the-same.
I’ve always used the two terms interchangeably.
Technically, “hot chocolate” might refer to that Hershey bar you left on your dashboard last August.
Cocoa is a powder consisting of cocoa solids and cocoa fat. There is no sugar or other flavorings. Hot chocolate can be made from cocoa, sugar and milk. Hot chocolate mix is cocoa, sugar, and sometimes it contains dried milk. It can also contain flavorings such as vanilla or cinnamon.
Cocoa can be substituted for baking chocolate if extra fat (such as butter) is added as well.
In our house, “hot chocolate” is made by dissolving ground sweet chocolate (like this) or a mixture of cocoa powder (like this) and sugar in boiling water. “Cocoa” is made by dissolving ground sweet chocolate or a cocoa powder - sugar mixture in heated milk.
Uh oh, now a new question is raised: I always thought the phrase was “one and the same.”
In everyday usage there is no difference, but in the recipes I’ve seen it looks like Cocoa is a little less sweet than chocolate.
Unfortunately, the column there is poorly researched, or maybe he just dealt with morons. (Either is perfectly plausible.) He was actually told the primary difference between the two, upon which all the other distinctions are but mentions thereof, and then he dismissed it for some reason.
The primary distinction between “apple juice” and “apple cider” is that Cider is not clarified. It still has lots of solids, which give it a more complex flavor and heartier texture. Strictly speaking, all cider is juice, but not all juice is cider. If you make apple juice at home, you probably will end up with cider. It’s probably true that cider tends to be made from earlier, tarter apples, but it doesn’t have to be and many varieties aren’t. Spiced ciders may use mellower apples and some spices.
Cider doesn’t last as (not even nearly) long as juice, even refrigerated (because of the solids). So I suspect that most companies clarify it in order to make distribution easier, and of course some people may prefer a lighter texture.
This is not a legal distinction, however, as noted. But that’s sort of irrelevant. There’s no legal distinction between pants and car keys, either. If you want to see the difference yourself, go to your grocery in the fall and look at plastic cider bottle. It will be much darker and with sediment at the bottom, whereas juice will be translucent. The difference between Juice and Cider is a little like the difference between White and Red wine.
Another distinction is that what’s sold as clarified apple juice is pasteurized, which contributes to its shelf life. Ciders have historically been unpasteurized, and the best ciders remain so. Lately with e. coli breakouts as a result of unpasteurized cider, pasteurization for ciders has been increasingly legislated, at least in my state. (Luckily it’s still available in raw form in certain places.)
You’re correct.
I may be missing something here but as I am someone who comes from the home of apple cider I thought the difference was obvious. Cider is alcoholic, juice is not.
In the United States, “hard cider” is alcoholic, “apple cider” is not.
Cough
Ahem, I agree with acsenray. Not that Hard Cider isn’t pretty great itself… 
There are separate recipes for “Hot Chocolate” and “Hot Cocoa” in the 1962 edition of “Joy of Cooking”; “Cocoa” is made with cocoa, while “Chocolate” is made with baker’s chocolate. The latter drink would presumably be richer, since it would contain cocoa butter and cocoa solids (“cocoa powder” is essentially just cocoa solids.)
You’re right. My occasionally gooberistic way of talking has now spilled over into an occasionally gooberistic way of thinking, which, unfortunately, sometimes trickles down into my writing.
“One-and-the-same” in TankTalk comes out “One-‘n’-the-same,” which got (incorrectly, no less!) transgooberated into “One-in-the-same.”
Technically, “Hot Chocolate” is made with chocolate and has fat in it.
“Cocoa” is made with cocoa powder, which does not have fat.
But the terms are used interchangably, and most people have never had real “hot chocolate.”
Oh! Well you learn something new everyday huh?! We don’t have that difference here. Cider (apple or pear) is alcoholic, juice is not.