It has always amazed me that a science field like Biology is so comfortable with so many definitions which are equivocal. (Life, Evolution, Species...) But that's just the way it is. Biology is the study of life, but biologists can't agree on a definition of life. In every text book that addresses this subject, they are all quite comfortable in stating that there is no unequivocal definition of life and they usually spend a significant effort in "proving" why we can't come up with an unequivocal definition.
I suspect this indoctrination has led most Biologists to give up on the definition. But not me! I believe it is possible to create an unequivocal, simple definition of biological life or for simplicity sake an organism. I have created this definition over a period of years, and it has been tested by a number of personally know scientists.
So here it is:
Life, or a living organism is a self contained entity which uses ATP (adenosine triphosphate) for metabolism and synthesizes ATP with enzymes which are synthesized from a genetic process requiring the transfer of information from DNA to RNA.
This definition covers all known life. It is short, and unequivocal. It is minimal. And it is easily measured. It does not use abstract terms. It is, however quite different from all previous definitions that I have reviewed.
So, at a minimum, a cell must be self contained, must metabolize, and must be a "protein factory". That's a summary, and it is the minimum requirement of any known living thing. Certainly living things also can do much more that this, and this is why this definition is minimal.
So, there it is, let's see what your thoughts are?