What Defines A Nightshade?

What Defines A Nightshade? Nightshade is a family of plants that includes tomatoes, eggplant, potatoes, and peppers. Tobacco is also in the nightshade family. Nightshades are unique because they contain small amounts of alkaloids. Alkaloids are chemicals that are mainly found in plants. What qualifies as a nightshade? Nightshade is a family of plants that