Hazard symbols are special symbols. They were made to warn people about dangers. Usually they are pictograms. Pictograms are small drawings that show what is happening (or what is going to happen, or what should happen) in a way that is easy to understand.
The European Union has made a few symbols that warn of dangers and that should be easy to understand. These are the hazard symbols for chemicals:
The 'n' in Harmful (Xn) stands for the French word nocif (harmful) and the Italian word nocivo (noxious).