Toxic describes something that is poisonous or harmful, like certain chemicals, snake venom, or spoiled food that could make you sick if you swallow it. Scientists mark containers of toxic substances with warning labels because even small amounts can damage your body. A toxic plant like poison ivy causes a painful rash when you touch it.

The word also describes harmful behaviors and relationships between people. A toxic friendship is one where someone constantly puts you down, spreads rumors about you, or makes you feel bad about yourself. A toxic environment might be a workplace where people treat each other cruelly or a classroom where bullying goes unchecked. Just as poison harms your body, toxic behavior damages people's feelings, confidence, and well-being.

When something is described as toxic, it means it causes harm, especially when you’re exposed to it again and again. One mean comment might sting, but a toxic relationship keeps hurting you repeatedly. The opposite of toxic is healthy or nourishing, whether you're talking about food that strengthens your body or friendships that make you feel good about yourself.