In A Nutshell
A legume is typically a pod with multiple seeds that will start to open on its own as it becomes ready for harvesting. A nut is typified by a hard outer shell protecting a single seed that we would call the “nut,” and does not open on its own. A drupe is basically a nut with a pulpy fruit around it. An example of a drupe whose nut seed you wouldn’t eat is a peach; one whose seed we would eat is an almond.
The Whole Bushel
While many people may know that a peanut is not a nut, you may not know what the distinction is between the different foods. Peanuts are often confused as nuts due to their name and the fact that they’re similar in taste and structure to most nuts available on the market. However, it is indeed technically a legume. Legumes often come in a pod and usual have multiple fruit in one pod. The pods that contain leguminous fruit will usually start to split when they are ready to harvest. Other examples of legumes include peas, carob, and just about any bean you can think of.
Nuts, on the other hand, are a different animal. Now, most nuts are presented in the supermarket with their shells already removed, but if we want to know how to classify a nut-like fruit, the shell is one of the most important ways to identify it. Unlike their legume cousins, nuts actually do not split open when they are ready to be picked—they stay shut tight until you force the delicious goodness inside out with a nutcracker, or an increasingly dented set of teeth. This is due to the nuts being surrounded by a hard outer shell. Also, nuts tend to only have one fruit inside as opposed to the several you would get in a legume pod. Examples of nuts that can truly fit the botanical classification are hazelnuts and acorns.
A drupe is the most interesting of them all. It turns out that many things we assume to be nuts (such as almonds or walnuts) are actually drupes. A drupe is a fruit that is pulpy on the outside, and has a hard shell on the inside that contains one seed. In most cases you eat the outer fleshy part of the fruit and discard the “stone.” Examples of this are drupes such as the plum, or peach, where you would never imagine eating anything but the flesh. However, in some cases the seed within the fruit, that most people would call a “nut,” is actually the part usually eaten. Of course, when working in the kitchen, very little attention is paid to the botanical differences.