Life/Mayr: in reality it is only the process of being-alive (as opposed to death) made to a thing, and does not exist as an independent entity! One can even attempt to explain that being-alive as a process can be the product of molecules that are not themselves alive.
Life: what is "life", has been strongly controversial since the 16th century. A group always claims that living organisms did not really differ from non-living matter: the physicalists.
Vitalists: living organisms have properties that inanimate matter lacks, which is why biological theories and concepts cannot be reduced to the laws of physics and chemistry.
Today it is clear that both groups were, in a sense, right and wrong.
Today: "Organism": unites the most useful from both and rejects the extremes.
Life/Mayr: can be synthesized in the laboratory. Principally open systems, therefore subjected to the second main sentence of thermodynamics.
Definition Life/Mayr: Activities of self-developed systems, controlled by a genetic program.
Definition Life/Rensch: Living beings are hierarchically ordered, open systems, predominantly organic compounds, which normally appear as circumscribed, cell-structured individuals of temporally limited constancy.
Definition Life/Sattler, 1986: an open system that replicates and regulates itself, shows individuality, and subsists on energy from the environment.
MayrVs: all contain superfluous and do not go into the genetic program, which is perhaps the most important. More description than definition.