I'd challenge that. Definitions are a lot fuzzier. I have yet to find a good definition of life that can last. I have had no problem adhering to the defitions of chemical and physical processes I learned when I was young.
Biology is the study of very complex things, so it's nearly impossible to limit the number of variables to only one. Most of what I see discussed as biology is either observation of the living and developing a story to try to explain its behavior, or biochemestry which is really chemestry.
Shalom.
One makes hypotheses and tests those hypotheses. It if the confidence one has with the results that differs. Sometimes the confidence limits are set at .0001. Othertimes the limits are much much higher (.10, .20 etc). The scientific method of hypothesis testing is the same across the sciences and one can NEVER EVER "prove" the null hypothesis.