A tourist takes a taste at Carmen winery in the Maipo Valley of Chile. (Martin Bernetti/AFP/Getty Images)

The vocabulary of wine can be perplexing, if not mystifying. Even wine lovers don’t always agree on what a particular word means. In fact, bitter debates can break out about why wine tastes bitter. And if we sound silly to each other, imagine what normal people think?

To help decipher some of that lingo, I asked my Facebook friends (who tend to skew toward the wine trade) for suggestions of words or phrases that could bear explanation. Many people suggested such terms as biodynamics, natural, minerality and malolactic fermentation, all of which I have written about before but obviously have not put to rest. A few suggested “structure.”

“Structure is one consumers always ask me about,” said Joe Herrig, a fine wine rep with Georgia Crown Distributing outside Atlanta.

Jon Bjork, a co-owner of Markus Wine in Victor, Calif., also suggested structure, or “good bones.”

“I had to get into the wine industry and chat with people while tasting before I finally understood what it meant,” Bjork said. “Before that, tour guides would say a wine had good structure, but I had no clue what they meant.”

Can wine have “structure”? It’s a liquid, after all, not a building. Without a glass, can, bottle, box or jug to hold it, it will spill on the ground and be lost forever. In a literal sense, “structure” doesn’t make sense. (And for that matter, why do we describe a liquid as “dry”? There’s no good explanation.)

I’ve probably used “structure” frequently to describe wines, as a shorthand for its tannin and acidity, two components that give wine complexity and longevity. I think of it as wine’s backbone, carrying the wine straight and true through life. But this discussion made me doubt myself, so I turned to the Great Big Book of Everything, also known as “The Oxford Companion to Wine.” Here’s “The Oxford’s” discussion of “structure,” in its entirety:

“Structure: Tasting term that refers not to any flavor but to the tannins, particularly their intensity. It may sometimes incorporate acidity.”

Well okay, so maybe I’m on the right track, though I certainly would always include acidity. But that’s hardly a definitive explanation. Elsewhere, in a section subtitled “How we taste,” “The Oxford” offers this: “The mouth is capable of making an overall assessment of a wine’s texture and structure, while the nose senses what we call its flavor.”

So structure isn’t something we taste, but something we feel when we swish a sip of wine around our mouths. When you read a tasting note describing a wine’s body, you typically see subjective terms that may or may not project the wine writer’s self image. A wine can be light, lithe, nimble, even svelte, or brawny, muscular, broad. It can also be flabby, flaccid, dull, ponderous. Silly as these terms may sound, they give a clue to the writer’s perception of the wine’s tannin and acidity, its structure. And they make for better reading than “good tannins” or “lacks acidity.”

As I wrote this, I sipped a 2016 Cotes du Rhone from Alain Jaume, called Haut de Brun. It’s a red blend of grenache, syrah and cinsault, made by a well-known producer in Chateauneuf-du-Pape. The flavors are textbook Rhone: scents of wild herbs, black cherries and berries, and a meaty, stony character. Those are the flavors. It also has good structure: Its tannins — the elements in the skins, stems and seeds of a grape that give the wine a drying characteristic on the palate and make your teeth itch as if you’d just eaten spinach — are firm but not overpowering. (If a wine makes you feel as thought you’ve just been whacked with a baseball bat, the tannins are too strong.)

But this wine’s structure is not just in the tannins. The acidity keeps everything else in check — it keeps the fruit flavors bright, and it refreshes my palate so that I want another sip. A good wine will always leave you wanting more. The structure — the combination of tannin and acidity — should also give the wine longevity. The importer, Kysela Pere et Fils, recommends on its website drinking this wine in one to four years. As much as I like it now, I’d rather revisit it in four or more years.

A night later, the wine had changed dramatically. It smelled like cloves. The tannins had receded and allowed the fruit flavors to shine, but the wine still had structure, because the acidity remained refreshing. While the tannins did not announce themselves, they were still evident on the wine’s finish.

White wines have structure, too. Sometimes structure is imposed on them, with new oak barrels that impart tannins. But acidity is really the key. The best example here would be a top-quality German Riesling where ample acidity balances an impressive level of sweetness that would turn any lesser wine into simple syrup with a kick. And those wines age amazingly well. Part of the attraction of skin-fermented white wines, which I wrote about last week, is that even the skins of white grapes impart tannins, and structure, to the wines.

I’ll go out on a limb here and disagree with the Great Big Book of Everything. Acidity is the essential key to structure in wine. Tannin is its partner.