Characters of Living

Reproduction is a character of living organism but it cannot be regarded as defining property because:-

_______is the defining character of all living organism

$ Exo-biology is a branch of biology. ! It deals with the study of external characters of the living organisms.

Virus introduction || living characters of virus || non living characters of virus || history of virology || structural components of virus || classification of viruses structures || important viruses (TMV, bacteriophage,HIV)

A virus is considered as a living organism and an obligate parasite when inside a host cell. But virus is not classified along with bacteria or fungi. What are the characters of virus that are similar to non-living objects ?