The class provides a simple list of criteria, which may not be correct, but is frequently used:
Life is based on chemistry; it is an ordered network of chemical reactions;
Life is a system that is not in equilibrium; it uses energy from its surroundings to organize itself;
Life is adaptive and self-optimizing;
Life is compartmentalized – it needs cells that act as enclosures and vesicles;
The molecules used by life are suited to environments with water.
The problem with this list is that some of the elements are open to interpretation. So Life is by definition, according to this, adaptive and self-optimizing. But what does it mean to adapt, to self-optimize. Does that imply if something changes in a way that isn't a movement towards perfectly optimized that it isn't life? What level of compartmentalization is needed? Can we think of the earth as one compartment? Does it mean a cells specifically or does the protein shell of a virus count?
I don't have a better idea about how to address the question "What is life?" but this list simply changes the single question to sub questions, two of which at least, are not really much easier to answer then the original question. This also precludes the possibility of synthetic life which may, or may not be fair.