Sanitary means clean and free from germs or conditions that could cause disease. A sanitary kitchen has been cleaned properly so bacteria can't grow on the counters or cutting boards. A sanitary bathroom has soap for handwashing and gets cleaned regularly to prevent the spread of illness.

The word comes from concerns about public health. In the 1800s, cities began building sanitary sewers to carry waste away from homes, which dramatically reduced diseases like cholera. Before modern sanitary systems, many people got sick from contaminated water and poor waste disposal.

Today we use sanitary to describe anything kept clean enough to protect health. Hospitals maintain sanitary conditions in operating rooms. Restaurants must follow sanitary rules about food storage and preparation. Even your school nurse keeps a sanitary environment by using fresh bandages and washing equipment between patients.

Something unsanitary is dirty or contaminated in ways that could make people sick. Leaving food out too long creates unsanitary conditions. Sanitary specifically refers to cleanliness that protects health, which is different from ordinary messiness or clutter. You might have a messy desk covered in papers and books, but that's different from unsanitary conditions where harmful bacteria or mold can grow.