What do viruses, viroids, and prions all have in common?

Virus:

1. It is a non-cellular, infectious entity with DNA or RNA as its genetic material and protein.
2. It is capable of reproducing only within the living cells of bacteria, plants, and animals.

Viroids: These are single-stranded RNA but do not have a protein coat.

Prions:

1. These are the proteinaceous infectious agents.
2. They are infectious due to abnormal folding and clumping.

Similarities:

1. Viruses, viroids, and prions are all acellular structures i.e. non-living.
2. They cannot reproduce on their own and are dependent on the host machinery to reproduce and continue their progeny.