Every once in a great while, I fall into the mood for some pedantic pontification. Nobody is asking for a blog post on this subject. But y'all are getting one anyway.
How often have you heard or seen the original (white box) D&D game referred to as "0th edition" or "0e"? Many times, I'd wager. I've used that label myself, often and without giving it a second thought. The Wizards.com website used to have an article on the history of D&D that called the Holmes Basic set "0" edition. The term still sometimes appears on the covers of OSR games too: "compatible with 0e" is used as a shorthand and a code phrase indicating compatibility with the 1970s D&D rules.
But when you stop and think about it, it's really wrong.
Why is OD&D sometimes called "0th edition"? Well, because it's the precursor to 1st Edition, meaning specifically Advanced D&D 1st Edition. And if you think in terms of "the world's most popular fantasy roleplaying game" (as the oft-repeated stock phrase goes), that makes perfect sense: OD&D is the direct ancestor of AD&D 1e, AD&D 2e, D&D* 3e, D&D* 4e, and ultimately D&D* 5e, so it's only natural to call the ur-edition "zeroth." Hell, if it weren't for that messy Basic–Expert–Companion–etc. branch of the D&D family tree, it would be a perfectly clear and indisputable linear progression from one game to the next.
This is, however, problematic in my view for a couple of reasons. For one thing, it subtly buys into the idea of "progress" from one edition to the next: that OD&D is nothing more than the unfinished prototype whence AD&D 1st Edition was fated to emerge, and (so the argument goes) by extension, 1st Edition is naught but the disorganized and unbalanced and needlessly restrictive mess of a game that must lead eventually and inexorably, step by step, improvement by improvement, one new and superior application of better game-design "technology" after another, to the present perfection that is 5th edition. At least until the new and improved 6th edition comes along, which will of course be better than 5th.
Hah. As if.
Just set aside for a moment the fact that every new edition of WotC D&D* appears to be fighting the previous edition's "battle" and overcorrecting for an old problem so as to create entirely new ones. Even if you ignore that whopper of an issue, it's abundantly clear—and has been for many years now, as previously articulated during the height of the OSR by voices as varied as Dan Proctor and James Maliszewski—that tabletop games aren't a technology and don't "advance" like one. So it's best, I think, not to lend undue support to that kind of thinking. It denies the simple fact that OD&D is a perfectly playable game in its own right, one that stands on its own just fine; and that this is also true of AD&D 1st Edition, and for that matter every other old edition of an RPG that's ever been superseded by a newer one.
And then, of course, there's the even more glaringly obvious problem: the basic logic of the matter. Even if OD&D is the immediate predecessor to AD&D 1st Edition (which it inarguably is), that doesn't make OD&D the 0th edition of Advanced D&D, because original D&D is not AD&D. OD&D can only be called "zeroth" in relation to its more popular Advanced descendants, but on its own terms, it's not a precursor or a prototype at all: it's just a game. The D&D game. Calling the white box "0e" makes zero sense from this perspective, because it's already the first edition of the game called Dungeons & Dragons.
Now, this realization is both obvious (indeed, almost trivially so) and a mild annoyance. Because it's impractical. We essentially cannot go around referring to white box OD&D as "1e" because everybody who cares even a little bit about old D&D editions already uses "1e"/"first edition" to refer only to AD&D 1st Edition. For the same reason, we are all of us forbidden—by the power of common usage and cultural convention, no less—from referring to B/X as the "2nd edition" of the D&D game, even though that's actually what it is. "2e"/"2nd edition" will always and forevermore refer only to AD&D 2nd Edition in the minds of gamers and grognards. (Though it is getting a bit of competition from Pathfinder 2e these days in some circles…)
And so it goes. When some uninitiated neophyte who only knows 5e and Critical Role—or, frankly, a veteran player with fifteen or twenty years of gaming under their belt who knows every obscure rule from 3.5 and Pathfinder—approaches my public game-table at the local comic shop and asks "what edition" of D&D I'm playing, they expect to be answered with a number between one and five. And then I feel obliged—even if I'm playing BECMI or running my game out of the Rules Cyclopedia—to say something wholly nonsensical and inaccurate (like "0th edition") in order to save both myself and my hapless interlocutor from a nerdy and eye-glazing explanation of red boxes and blue boxes and Basic Sets.
It's tiresome. It's annoying.
• • •
If I had my druthers, I'd call the games what they call themselves. I'm a fan of that: using the names that appear in the actual text. And, heck, it's been a while since I've done the "English major" thing. So let's go to the text.
We can't start with the white box, because of course the white box only ever refers to itself as Dungeons & Dragons, never giving any inkling or indication of successor editions. AD&D 1st Edition only rarely refers back to the "original D&D" game, but when it does, the word "original" is just a modifier, lower-case and not boldfaced, so it's set apart from the title of D&D: in the 1st Edition books, there are only the frequent self-references to Advanced Dungeons & Dragons and the sparse and occasional references to the original Dungeons & Dragons (or to one of its specific volumes or supplements).
Concerning the proper names for the two TSR-published AD&D editions, I was surprised to note (when I started researching the topic) that the first edition of the game is referred to as Original [Edition] Advanced Dungeons & Dragons in the text of the 2e books more frequently than it's referred to with any variation on "first edition." The 2nd edition, of course, is called "Advanced Dungeons & Dragons 2nd Edition" all over the place (including on the covers), with that capital "E" marking the edition number as a formal part of the game's title. But for first edition, well…
You can see an example of this in the AD&D 2e preview document, which refers to AD&D 2nd Edition in this formal fashion, but "first edition AD&D" more informally.
By the time of the PHBR splatbooks, though, we have both "Original Edition" and "1st Edition" being used more or less interchangeably when referring back to the older rules. So it would seem that as far as AD&D 1st Edition goes, both "AD&D 1e" and the somewhat less common "OAD&D" are equally correct (and official).
Things get a little bit more interesting when we turn our attention to the Cook/Marsh Expert Set. This volume, on page X4, refers to the Moldvay Basic Set several times as the "2nd Edition" of D&D Basic—which, of course it is, as the Moldvay Set has replaced the Holmes Set as of 1981. But curiously, this is also the only place anywhere in the text of any Classic D&D rulebook where any part of Classic D&D is referred to with an edition number. So B/X straight up calls itself "2nd Edition"—but, tellingly, BECMI never, ever calls itself "3rd"!

There are (as I've mentioned on this blog before) a few spots where BECMI refers to itself in relation to other (A)D&D editions. On page 63 of the Mentzer Basic Players Manual, the red box edition very clearly calls itself "the original DUNGEONS & DRAGONS game" (as distinct from AD&D)! Whereas on the inside front cover of the Mentzer Expert Set, it uses the term "Original Set" to refer to the 1974 white (or woodgrain) box rules—and also spells out quite clearly that just as the newly revised 1983 Basic Set is the official replacement for the Holmes and Moldvay versions, the 1983 Expert Set has officially replaced both the white box and the Cook/Marsh Expert Set as the current version of the D&D game. The text of the 1983 Expert Set establishes itself as the inheritor of OD&D—not as a 3rd edition OD&D, mind, but as a revision to the (Moldvay/Cook) 2nd edition of (O)D&D.
That's what BECMI is, when you get right down to it: it's OD&D 2nd edition, revised. D&D v2.1, if you'll pardon my hateful use of version numbers (or D&D v2.5 if you happen to be clueless about how version numbers work).
And then of course there's the Rules Cyclopedia, which (despite the fact that it does indeed make numerous small tweaks to the rules and content of the boxed sets that it collects and reorganizes) is never treated by its own text as a "new" edition of D&D. You could think of it as OD&D v2.2, I suppose, but really it's just BECMI all over again—or at least, that's what the book itself would apparently like the reader to believe.
• • •
So where does all of this mess leave us? Well, I think it affirms that there are fundamentally four distinct versions of TSR (O/A)D&D. AD&D 1st Edition and AD&D 2nd Edition are obvious, they get called that by the text of AD&D and also by everybody who still cares to discuss them. But there are also Original D&D and Classic D&D. Original D&D—the 1st edition of D&D—consists of the original white box, the four or five supplements, and the Holmes Basic Set (which both serves as an introduction to the rules and frankly fills in a lot of gaps in the white box, making it complete enough to be playable). And Classic D&D—that is, the 2nd edition of D&D—consists of the magenta Basic Set and cyan Expert Set, followed by the 2nd edition revised, which is BECMI and all of the 80s and 90s D&D supplements and rulebooks that followed (including the Rules Cyclopedia).
Is that useful for talking about these various D&D versions in online forum discussions? No; not at all. People everywhere will still know them as B/X or Mentzer or whatever labels are in vogue at the moment. But for me? While it's a bit funny to realize of a sudden that I'm both an occasional AD&D 1e referee
and a frequent OD&D 2e referee (huh… I'm a 2nd edition DM after all… imagine that…), I still recognize that there's no point in futilely trying to get all the old-school D&D players thinking of B/X and BECMI as "OD&D 2nd edition" (even though it is). So I'm going to continue to refer to these two versions of the D&D game as
white box D&D and
red box D&D (or, when the distinction is necessary,
white box OD&D and
red box OD&D)—because it's accurate enough, it's clear enough, and it's what we actually called these games back in the 90s.
Though it would be nice, I suppose—if only as a courtesy to all the other tabletop roleplaying gamers out there—if the labels "1e" through "5e" absent other context didn't automatically refer to an AD&D or D&D* edition. After all, lots of other RPGs have numbered editions. Even Pathfinder now. Maybe the frequent references to PF1e and PF2e will force people discussing AD&D 1e and 2e to be more precise when circumstances demand it. That might just open the way for broad acceptance of my OD&D 1e and 2e labels after all. (But I doubt it.) ∎