They are infectious agents that replicate inside a host's body.
They are neither living nor non-living.
They are non-living because they do not use their energy for survival. They only become active when they come into contact with a host cell. Once activated, they use the host cell's energy and tools to make more viruses.
Examples- adenovirus, Hepatitis C virus, etc.
Composition of virus:
They usually lack a cell wall.
Instead are surrounded by capsid (a protective protein coating)
They contain either RNA or DNA as the genetic material.
They utilize the hosts' machinery to replicate and transcribe their genome.
Viruses are non-living because they cannot multiply without the living cell and they do not possess a cellular structure.