Which of the following best defines the term "contaminate"?

The term "contaminate" is best defined as to make an object unclean or unsterile. This definition accurately reflects the idea that contamination involves the introduction of harmful substances or microorganisms to a previously clean environment or object, compromising its sterility.

Understanding the context of contamination is important in fields such as healthcare, food safety, and laboratory practices. Contaminated surfaces or materials can lead to the spread of infections, disease transmission, or compromise the integrity of experiments.

In this context, the other options do not accurately embody the concept of contamination. Reducing the presence of pathogens and isolating harmful microorganisms are actions aimed at preventing or controlling contamination, rather than defining it. Sterilizing through heat refers to a method of eliminating all forms of microbial life and is the process used to achieve a clean state rather than the act of making something unclean.