|A nonliving infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.
|an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host’s expense.
|an animal or plant on or in which a parasite or commensal organism lives.
|one billionth of a meter
|a substance used to stimulate the production of antibodies and give immunity against one or more diseases, prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease.