A "biological hazard" or "biohazard" refers to a pathogen, especially one used in or produced by biological research. Some examples are medical waste or microorganism samples. It can also mean the health risk posed by the possible release of such a pathogen into the environment.
The word "biohazard" combines the prefix "bio-" with "hazard." "Bio-" originates from the Greek word "bios," which means "life." "Hazard" entered the English language around the year 1300 from the Old French word "hasard," which refers to a game of chance played with dice. In English, "hazard" took the sense of meaning riskiness in the 1540s.