Homeostasis
I think life definitions must include self-maintenance. Living things have self and not-self in a dynamic equlibrium. Crystals replicate but have no mechanisms of maintenance. Fire likewise. Clouds, another semi-living system, do have a kind of internal self-coherence, but no replication. Viruses, because of their encapsulation and DNA/RNA self-definition, have the self/not-self distinction, but of course lack the machinery of replication. Though a recent virus find has more genes than expected so perhaps we should say viruses have implicit self-replication.
Adam