A virus is a biological partical incapable of reproduction on its own. Once inside a living cell it reproduces.
A virus is non-living yet it reproduces so you could think of it as in between living and non-living.
A virus is extremely small - 20 to 400 nanometers. It hass an extremely simple 'anatomy'; only a small piece of single or double stranded DNA or RNA in a protein capsid. Capsid amounts to ~95% of the virus and gives the virus it's particular shape.
