What Exactly is a Fruit?

by Izaak

I.

Many of the people reading this article may be under the impression that a tomato is actually a fruit. It’s perhaps the most frustrating of wrong trivia, because it isn’t entirely wrong. This pseudomisinformation leads to all sorts of random questions, many of them silly and obviously wrong.


A lot of what I’m going to talk about in the first section is a specific example of the ideas already expressed in these two blog posts; Words as Hidden Inferences and Disguised Queries.

For those of you who don’t want to read the two posts I mentioned above, the basic idea is that the words we use don’t always translate perfectly to the real world. They refer to categories of objects that share similar features, but that aren’t exactly the same. The other important idea is that when we ask whether something is a <noun>, we often don’t care whether an object really is or isn’t in that category—we have a separate question that we really care about.

So that’s where the philosoraptor went wrong. The question isn’t “Is a tomato a fruit?”, the question is, “Is ketchup a smoothie?” Which it obviously isn’t. We can answer every question people have, upon “finding out” that tomatoes are a fruit, extremely easily by applying this technique. Is salsa a fruit salad? No, obviously not.

But wait, you say, you haven’t answered my question. Is a tomato a fruit or not? Well, remember that the word fruit is just a category of things that share similar features. So let’s talk about the features of things we call fruits:

Comes from a plant? Yes
Edible? Yes
Sweet or sour? No
Juicy? Yes

So we see that out of the main features that fruit have, being sweet or sour, the tomato doesn’t in fact have. And that’s the major reason why it doesn’t belong in the category of fruit.

II.

Now I’m sure that some of you are thinking, isn’t the definition of fruit anything that has seeds? And so here’s where the pseudomisconception comes from. Tomatoes are, in one way, fruit. And the reason for this is that there are two words, fruit and fruit, that look the same, sound the same, but mean different things. Sometimes, people will try and use words like this to make fallacious arguments; when this happens, it’s called equivocation.

Here’s an example of a syllogism (an argument which uses two facts to logically come to a conclusion) that exhibits equivocation:

A feather is light.
What is light cannot be dark.
Therefore, a feather cannot be dark.

The problem with this argument is that light can mean two different things- and so can the word fruit. Meaning one is a sweet, juicy, edible plant, and meaning two is the part of a plant that contains seeds. These are called the culinary definition, and the botanical definition, respectively.

There is also an important distinction between the culinary definition of the word vegetable, and the botanical definition of the word vegetable. Namely, there is no botanical definition of vegetable; the word means nothing, whereas we are already familiar with the culinary definition: they’re plants we eat that aren’t nuts or grains or (culinary) fruit.

So, back to the main point, we have these two different definitions of the word fruit; one which refers to a collection of foods that we treat as being in the same category for the purposes of cooking, and one of which refers to a botanical concept relating to the the way plants reproduce. Tomatoes happen to fall in one of these categories, and not in the other.

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Using this Venn diagram we can start to figure out what belongs in which category. Tomatoes are in the light blue (cyan) area; they are culinary vegetables, and botanical fruit, but not culinary fruit. They are joined by a lot of other plants; green beans, eggplants, cucumbers, and chili peppers are all in the light blue area.

In the yellow area we find the traditional fruits. Raspberries, mangos, peaches, apples, oranges, you name it. They all are parts of plants that surround seeds, and they are all used as fruits while we cook.

In the purple or magenta area, we find nothing. There are no foods that are both culinary vegetables, and culinary fruits. Unlike the culinary fruit vs botanical fruit distinction, or the botanical fruit vs culinary vegetable distinction, foods are either culinary vegetables or culinary fruits. There is no food that is both. A consequence of this is that nothing can be in the white section, either.

In the blue area, we find the rest of our vegetables. Carrots, lettuce, potatoes, most herbs, spinach, and celery. Anything that’s a leaf, root, or stalk, basically.

In the green area, we find botanical fruits that aren’t vegetables or culinary fruits. Examples include grains, nuts, seeds, beans, and of course any fruits that aren’t edible.

The red areas presents a very interesting question. Are there any culinary fruits that aren’t botanical fruits? Think for a moment, see if you can come up with any.

III.

You probably can’t, and there’s a reason for that; most, if not all, culinary fruit are also botanical fruits. Why? The answer lies in the evolutionary purpose of fruit, and to talk about that, I have to go into more detail about the botanical definition of fruit.

Here is a picture of a typical fruit. Some fruit have more than one seed, but the main idea is the same. What we have been calling the botanical definition of fruit is really just a more layman friendly word for the pericarp. One note—epicarp is also used to mean the same thing as exocarp.

In some plants, such as grasses, the pericarp is fairly small. This is because the purpose of the pericarp in this plant is similar to the purpose of a yolk in eggs—to feed the baby plant at the very beginning of it’s growth. However, this food also is very useful for herbivores, who can eat the pericarp and seed and gain the nutrition from it. In some cases, however, plants found that being eaten by an herbivore, carried around to a new spot, and deposited there gave them more resources and less competition, increasing their genetic fitness. This means that plants with genes that helped their seeds be eaten by predators passed on more and more of their genes, which eventually led to the evolution of sweet, juicy plants.

What does this have to do with why most culinary fruits being botanical fruits? All I’ve shown so far is why it’s advantageous for botanical fruits to be culinary fruits in some cases. But imagine a plant that creates a fruit-like structure somewhere that doesn’t surround a seed? The herbivores would eat it, and the plant wouldn’t benefit. In fact, the plant would suffer, because it would have wasted nutrients and resources on a completely useless task- so any plants that did this would have a massive decrease of fitness, and wouldn’t be able to reproduce as easily.

IV.

But still, it’s strange that there are no plants that are culinary fruits without being botanical fruits. Are there really none?

Well, there is one. But it’s surrounded by controversy. You see, there is one plant that is not categorized as a botanical fruit, but is used while cooking almost exactly like a fruit. This plant is rhubarb.

Now, rhubarb looks almost nothing like the other fruits in our life. But is that because rhubarb is not a botanical fruit (it’s not), or is it because rhubarb is not a culinary or botanical fruit? I for one think rhubarb fits in with the culinary fruits. And a New York court ruling from 1947 agrees with me.

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