A selection of natural wines at Grand Cata, a shop specializing in wines from Latin America. (Hannah Wagner/For The Washington Post)

What exactly is natural wine? Depends on whom you ask.

Because the term has no legal definition, you can put that question to two different people — a clerk in a wine shop, for instance, and a sommelier — and get two different answers. According to Jorge Riera, wine director at the New York restaurant Frenchette, “the most essential thing to know is how all these wines are farmed.” In many natural vineyards, Riera explains: “All the work is done manually, no machinery is used. They may use tractors to plow, and a lot of them use animals. They often plant herbs between the rows.” The most important work takes place in the vineyard, Riera says, and not inside the winery building. “It’s the most beautiful symbiosis of insects, herbs, flowers — and the farmers are working in a healthier way.”

Is natural wine organic? Often, yes. Is it also biodynamic? Sometimes. But it is almost always made with minimal intervention. Here are a few helpful definitions:

Organic: In organic winemaking, grapes are typically grown without pesticides or other chemicals. Beyond that, it gets complicated. Many small wineries operate in the spirit of organic agriculture, without being legally certified as organic. Even the precise definition of “organic” varies, between, say, Europe and the United States.

Biodynamic: Biodynamic farming — developed and promoted by the controversial Austrian Rudolph Steiner (1861-1925), also considered the intellectual father of the Waldorf educational philosophy — typically incorporates organic practices. According to Steiner, everything is connected, from the grape to the soil, which is itself considered a living organism. Biodynamic winemakers often use special herbal sprays and composts, and time their harvests to the lunar calendar.

Minimal intervention: At its most basic, wine is what you get when the wild (or indigenous) yeast on the skin of grapes converts the sugar inside the fruit to alcohol. That’s it. Minimal intervention is a relatively radical winemaking approach that tries to do as little as possible beyond that. In much of the winemaking world today, there are nearly 200 commonly used — and entirely legal — additives: sugar to increase alcohol content; inoculated (or commercially cultured) yeast to kick-start fermentation; sulfites as a preservative; gelatin for texture; colorants; antimicrobial agents; and other ingredients.

Sulfites: Sulfur dioxide compounds, or sulfites, occur naturally in the winemaking process. But adding even more of the stuff as a preservative — a process known as sulfuring — is a topic of some debate in the natural wine community. Some natural vintners adhere to a zero-added-sulfite policy, while others add only a tiny amount. Any wine containing more than 10 parts per million of sulfur dioxide must include “contains sulfites” on the label. Sulfites, in some people, can cause asthmalike symptoms and congestion.