• Noncellular nature: Viruses are acellular entities, meaning they do not possess a cellular organization (like cytoplasm or organelles).

• Inert crystalline structure: Outside of a host cell, viruses exist as inert particles. They can be purified and form crystalline structures, showing no metabolic activity until they come into contact with a living host cell.

• Obligate Parasites: Once they infect a living cell, they hijack the host's machinery to replicate themselves.

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