What the Heck Is a "Medium" Onion, Anyway?

When you start out cooking, measuring everything exactly can be a big concern, which is why beginning cooks may be put off by recipes that list vague amounts like “a pinch of salt,” or “one medium onion.” Though “pinch” has been pretty much standardized—it’s agreed upon to be an 1/8th of a teaspoon—a “medium” onion is…