Bacteria/bækˈtɪriə/ Definition 1 of 3Pro Tip 1/3Health Hazard Often implies danger, especially in health-related contexts. Always wash hands to avoid bacteria that cause sickness. Pro Tip 2/3Invisible Threat Reminds that bacteria are not visible, causing unseen risks. Microscopes reveal the bacteria lurking on surfaces. Pro Tip 3/3Disease Link Important in conversations about hygiene and infections. Doctors prescribe antibiotics to fight bacterial infections.