Who doesn’t love a pedantic houseguest? Next time you’re at a dinner party and someone breaks out the mixed nuts, seize the moment and let everyone know that a lot of the tasty treats we call nuts don’t actually merit the title. Botanists define a “nut” as a dry, one-seeded fruit encased in a hardened ovary wall (called a pericarp). Genuine nuts are fused to their shells and won’t naturally break open upon reaching maturity. Hazelnuts fit the criteria. So do chestnuts. But these ever-popular snack foods sure don’t.

1. Peanuts

The star ingredient of America's favorite nut butter isn't actually a nut. Instead, peanuts are considered legumes, along with soybeans, lentils, and chickpeas. Unlike nuts, most legumes come in self-opening pods—which may or may not grow underground, depending on the species. 

2. Almonds

These almonds formed inside a fleshy fruit.onairjiw/iStock via Getty Images Plus

Almonds are seeds found within the fleshy, peach-like fruits of the Asian Prunus dulcis tree. They’ve earned a spot on our list because actual nuts don’t come wrapped up in softened fruit matter. So how do botanists classify almonds? As drupe seeds. Briefly stated, a drupe is a soft fruit with a hard inner shell. (Think peach pits.)

3. Cashews

Like almonds, cashews are drupe seeds pulled from soft fruit packages. The trail mix staples poke out of red, yellow, or green “cashew apples” that grow on South American trees. Cashew seeds are naturally protected by a toxin-coated outer shell that's roasted to neutralize the acid. In spite of this defense mechanism, the yummy snacks were soon embraced by Portuguese explorers and distributed across the globe.

4. Walnuts

The walnuts this squirrel is noshing on are drupes, not nuts.Serhii Ivashchuk/iStock via Getty Images Plus

Hey look, it’s another member of the drupe clan! Walnuts inhabit green fruit on temperate trees in the genus Juglans. Most of the seeds that end up on American dining room tables come from the English walnut tree, Juglans regia [PDF]. Even if you don’t eat the drupes, you can probably find a use for them: Walnut shells have been incorporated into everything from cosmetic products to kitty litter.

5. Pine nuts

About 20 pine tree species—including the Italian stone pine—produce big seeds that get harvested en masse. Those seeds are removed from cones in a meticulous process, which accounts for their high selling prices.

5. Brazil Nuts

You’ll encounter Brazil nuts all over the Amazon rainforest, in such countries as Peru, Colombia, Venezuela, and (of course) Brazil. They come from a hardened 4-to-6-pound pod containing up to two dozen seeds that might become trees someday. The pods are so hefty, getting bonked on the head by a falling one is enough to stun or even kill you.  Surprisingly, Brazil Nuts can also be fairly radioactive thanks to the trees' roots, which grow deep within radium-rich soil.

7. Macadamia Nuts

An Australian macadamia orchard filled with the country's native drupe. oxime/iStock via Getty Images Plus

Gympie, Queensland, has an odd claim to fame: Approximately 70 percent of all the macadamia nuts on Earth are descended from trees grown in the Australian town. Macadamias are an ecological staple in Queensland and New South Wales. But—stop us if this sounds familiar—their so-called “nuts” are drupes.

8. Pistachios

Not only are pistachios drupes, but they’ve got shells that automatically open with a literal popping noise once the contents reach a certain size. When all’s said and done, though, at least pistachios are Frank Drebin-approved.

9. Pecans

The Algonquian term for “nut that requires a stone to crack” gave us the English word pecan. Wild pecans can be gathered in Mexico and the United States—they’re true North American treasures. Name origin aside, they can’t accurately be called nuts. Botanists usually refer to them as drupes, but because of their tough shells, the label “drupaceous nuts” might be more appropriate. Either way, pecans aren’t true nuts. They make for great pies, though.

10. Coconuts

This cheeky monkey seems to be enjoying its delicious drupe.Volga2012/iStock via Getty Images Plus

A drupe of unusual size, the coconut is a fibrous juggernaut that bears a single seed. The whitish fleshy interior can be immersed in hot water and then rung out through a cloth to produce coconut milk. Meanwhile, the outer shells are responsible for some of the most delightfully bizarre Guinness World Records categories, such as “most green coconuts smashed with the head in one minute.” (You can see other unusual Guinness World Record categories here.)