To contaminate means to:

To contaminate means to make something unclean or unsterile. This definition is grounded in the context of microbiology and infection control, where contamination refers to the presence of unwanted or harmful microorganisms on a surface, object, or within a substance. When something is contaminated, it becomes a potential source of infection or illness.

In healthcare and other environments where cleanliness is paramount, the goal is often to maintain sterility and eliminate contaminants to prevent the spread of disease. Understanding contamination is crucial for implementing proper hygiene practices, including handwashing, sterilization of instruments, and maintaining a clean environment.

The other choices do not align with the definition of contamination—making something clean or sterile would be the opposite effect, while reducing bacteria does not equate to introducing contamination. Providing a portal for entry pertains more to the route through which pathogens can enter a host rather than the concept of contamination itself. Understanding these distinctions is key in maintaining safety and health standards.