To sterilize something means to make it completely free of germs, bacteria, and other living microorganisms that could cause infection or disease. Hospitals sterilize surgical instruments by heating them to extremely high temperatures or using special chemicals, ensuring that no harmful bacteria remain. When doctors sterilize equipment before an operation, they're making it so clean that not a single living germ survives.

The process goes far beyond ordinary cleaning. Washing your hands with soap removes most germs, but sterilizing something eliminates all of them. Scientists sterilize laboratory equipment before experiments to ensure that no unexpected bacteria interfere with their results. Before astronauts brought moon rocks back to Earth, NASA had to figure out how to sterilize them, since nobody knew if alien microbes might exist.

You might also hear sterilize used in a different context: to sterilize soil means to heat or treat it to kill seeds and organisms before planting, giving your chosen plants a fresh start. Canning factories sterilize jars before filling them with food so the contents stay safe to eat for months or even years.

The noun form is sterilization, and something that has been sterilized is called sterile.