If you have just been bitten by a terrifying snake, this is not the article for you. If you're hustling to the hospital with twin puncture wounds in your shin and Googling for remedies you can do in the passenger seat of the car while your friend frantically drives you into town, keep scrolling those search results. By the way, you're doing great. Don't forget to breathe.
Nor will this article delve into the relative qualities of "Toxic" by Britney Spears or "Poison" by Bell Biv DeVoe, though that is a piece of cultural criticism the world could use.
What this article will provide is the ammunition you need to win that argument on social media or with your know-it-all cousin. Because you're right: Poisonous and venomous do not mean the same thing.
Who's Doing the Biting?
Poisonous creatures and venomous creatures are both bad news as they both involve toxic substances that cause physical effects. The delivery of that toxin is what makes the difference. Poison is passive: You have to bite or touch the animal for that animal to deliver its toxin. Venom is active: The creature has to bite you (or sting or poke you) for the toxin to get into your body.
So the aptly named poison frog, which secretes a toxin on its skin, has to be touched or licked to harm its enemy. The pufferfish, which is famously poisonous but edible, has to be prepared meticulously in order to be eaten. Poisonous animals and mushrooms are often brightly colored as a warning to predators: Don't eat or touch me!
Not all toxins are the same. Some only make a creature taste bad, like the monarch butterfly, though others are incredibly lethal, like the toxins from the golden poison frog or fly agaric mushroom.
A Toxic Who's Who
A rattlesnake is venomous because it fills its fangs with its toxin and directly injects that into its foe. The platypus, maybe surprisingly, is also venomous. The males have spurs on their ankles that they use on predators.
There are even a few creatures that are both venomous and poisonous. The blue ringed octopus is one of those lucky few. It has a venomous bite, but if that doesn't stop predators from trying to eat it, it's also poisonous once it's in their belly. Yikes.
Some people believe mongooses are toxic, but actually they're just better at handling toxins than almost any other animal on the planet. They kill and eat notoriously venomous snakes like cobras. Armed with your new knowledge, you can probably see the trick now. Cobras are venomous, not poisonous. So the mongoose is ingesting the cobra's toxin, which gets broken down by the acids in the mongoose's stomach. Also, the mongoose can tolerate a little bit of snake venom.
Even plants can be counted as venomous or toxic. Poison ivy is correctly named, as its toxin is delivered by merely touching its leaves. Stinging nettles are venomous, if you're being generous with the term, because they deliver their irritating toxin via spines.