Some of the characteristics of life are the ability to grow and develop, ability to reproduce, metabolism, homeostasis, response to stimuli. Viruses have some of those characteristic, but some of them do not. Still, those characteristics they share with the other "confirmed" living organisms they fulfil only when they are inside the host cell, for example, reproduction in the content of replication of genetic material. However, they have no metabolism nor reproduction on their own and the host cell is important for them.