Here's why:

* Nucleic acid: Viruses contain either DNA or RNA as their genetic material.

* Protein coat: This coat, called a capsid, protects the nucleic acid and helps the virus attach to host cells.

* Host machinery: Viruses lack the machinery to replicate themselves. Instead, they rely on the host cell's ribosomes, enzymes, and other resources to create new viral particles.

Let me know if you have any other questions!