When scientists use these words, they typically mean something completely different than what they do when non-scientists use them. Sometimes our definitions are too narrow or too broad, and sometimes, we use terms interchangeably when they actually shouldn't be. We dug deep into the American Museum of Natural History's website to help set the record straight.

1. and 2. Poisonous and venomous

Though the words poison and venom are often used interchangeably—and although they both describe a toxin that interferes with a physiological process—there is a difference. It’s all about how the substance is delivered: Venom is delivered via an anatomical device like fangs, while poison is usually inhaled, ingested, or absorbed. As Mark Siddall, Curator of Invertebrate Zoology at AMNH, explains in the clip above, both the rough-skinned newt and the blue-ringed octopus produce a powerful toxin called tetrodotoxin. But scientists call the octopus venomous because it delivers the substance through a bite, and consider the newt poisonous because the toxin is in its skin.

3. Microbes

When most people hear the word “microbe,” they think of stuff that they can't see that's going to make them sick. But while some do cause disease, not all microbes, or microscopic organisms, are bad; in fact, some are essential for life. Microbes include bacteria, viruses, fungi, and protozoa, and make up most of the life on our planet. For every human cell in our bodies, there are about 10 resident microbes; only a small percentage are pathogens.

4., 5., and 6. Meteor, meteorite, and asteroid

Although some use these terms interchangeably, meteors, meteorites, and asteroids are all different things. Here’s how to use them correctly: Asteroids are the rocky bodies that orbit the Sun mostly between Mars and Jupiter; they’re much smaller than planets, and they're sometimes pulled out of their orbit by the force of Jupiter’s gravity and travel toward the inner solar system. The vast majority of meteorites—rocks that fall to Earth from space and actually reach the Earth's surface—are parts of asteroids. Like meteorites, meteors are objects that enter Earth’s atmosphere from space—but they’re typically grain-sized pieces of comet dust that burn up before reaching the ground, leaving behind trails that we call “shooting stars” as they vaporize.

7. Theory

When most people use the word theory, they're talking about a hunch or guess. But for scientists, a theory is a well-substantiated—and testable—explanation that incorporates laws, hypotheses, and facts. The theories of gravity and evolution, for example, aren’t mere hunches; they explain why apples fall from trees and how so many very different plants and animals exist, and have existed, on Earth. According to AMNH’s website, “A theory not only explains known facts; it also allows scientists to make predictions of what they should observe if a theory is true.” Scientific theories are also testable; if evidence isn’t compatible with a theory, scientists can either go back to refine the theory, or reject it altogether.

8. Fossil

As Lowell Dingus, a research associate at AMNH, explains in the video above, fossils aren’t just the remains of hard parts like bones, teeth, and shells. Under the right conditions, organisms’ soft parts—like skin impressions and outlines—can also fossilize. Other things that qualify as fossils are traces made by organisms, like footprints, burrows, and nests. Fun fact: By most definitions, in order to qualify as a fossil, the specimen must be more than 10,000 years old. If they’re younger than that, the specimens are called subfossils.

9. Common ancestor

When you use the term common ancestor, you might mean that one creature evolved from another. But that oversimplifies it: Humans didn’t evolve from monkeys, for example, but share an ape-like common ancestor with Old World monkeys. According to AMNH's website, "Overwhelming evidence shows us that all species are related—that is, that they are all descended from a common ancestor. More than 150 years ago, Darwin saw evidence of these relationships in striking anatomical similarities between diverse species, both living and extinct. Today, we realize that most such resemblances—in both physical structure and embryonic development—are expressions of shared DNA, the direct outcome of a common ancestry."

10. Hominins

Homo sapiens are the only remaining descendants of a once-varied group of primates called the Hominini. You’re probably used to using the term hominids to refer to humans and their ancestors, and not long ago, you would have been correct—but recently, the definition of that word has expanded to refer to all great apes and their ancestors. Instead, you should be using the word hominins to describe the group comprised of modern humans, extinct human species, and our immediate ancestors.

The first hominin fossil was discovered in 1856, and since then, many hominin fossils, comprising many different species, have been discovered. These species emerged in different places over the past six or seven million years, and some of them even lived simultaneously, as AMNH’s Dr. Ian Tattersall explains in the video above.

11. Dinosaurs

We typically say that all dinosaurs went extinct 65 million years ago, but that’s not actually the case. In fact, if you look out your window, you might see one right now. Birds descended from the common ancestor of all dinosaurs, and so, "just as humans beings are a kind of primate, birds are a kind of dinosaur," Mark Norell, curator of the Division of Palentology at AMNH, explains in the video above. So go ahead: Tell your friends that pigeon is a dinosaur. They'll never look at those birds the same way again.

12. Pterosaurs

Chances are, you probably haven't been using this word much at all. That's because most of us grew up thinking that pterosaurs like the pterodactyl were dinosaurs, and that's what we called them. But these animals weren’t dinosaurs, and they weren’t birds, either. They were actually flying reptiles, cousins to the dinosaurs that evolved on a separate branch of the reptile family tree. Pterosaurs were the first animals after insects to evolve powered flight by flapping their wings to generate lift; you can find out more about pterosaurs from the video above.

13. De-extinction

You probably understand what de-extinction is, but you might not understand what kinds of animals we can bring back—and you have Hollywood to thank for that. Despite what you saw in Jurassic Park, scientists will never be able to resurrect non-avian dinosaurs from extinction; any DNA that might be found is just too old to be used. But for other species, science might find a way in the not-too-distant future. In fact, in 2003, researchers implanted a goat egg with genes from an extinct Spanish mountain goat and used a goat-ibex as a surrogate; the resulting animal lived for just a few minutes, but the experiment proved it could be done.

Scientists expect that technological breakthroughs—and genetic data gathered from specimens—will provide ways to revive recently extinct species (think passenger pigeons, and maybe even wooly mammoths). It sounds cool, but de-extinction comes with a number of thorny scientific and ethical questions, as Museum Curator Ross MacPhee explains in the video above.