Viruses are not classified as prokaryotes or eukaryotes primarily because they differ fundamentally from cellular life forms. Prokaryotes, such as bacteria, are single-celled organisms that lack a nucleus and other membrane-bound organelles. Eukaryotes, on the other hand, can be single-celled or multicellular and have a well-defined nucleus and organelles.
Viruses, however, are acellular. They do not possess the cellular structures that define prokaryotes and eukaryotes. A virus consists of genetic material (either DNA or RNA) encased in a protein coat, and some have an additional lipid envelope. Unlike living cells, viruses are unable to reproduce independently. They require a host cell to replicate and propagate, hijacking the host’s cellular machinery to produce new virus particles.
Furthermore, viruses do not carry out metabolic processes on their own, which is a key characteristic of life. This lack of cellular organization and independence from cellular functions places viruses in a unique category, distinct from both prokaryotic and eukaryotic organisms.