Avirulent

Part of speech: adjective

Definitions

1. Referring to a biological entity that lacks the capability to cause illness or trigger a harmful reaction in a living host
2. Describes an organism or substance that does not produce harmful effects or illness in a host
3. Pertaining to a pathogen that cannot induce disease symptoms in infected individuals

Etymology: "Avirulent" is a plain compound: the prefix "a-", meaning "not" or "without", joined to "virulent." The prefix comes ultimately from ancient Greek "a-" (the negating prefix, as in "atypical" or "amoral"), which English has used for centuries to turn adjectives into their opposites. So "avirulent" literally means "not virulent." The base word "virulent" comes from Latin "virulentus," meaning "full of poison" or "poisonous," built on "virus," which in Latin meant a slimy liquid, poison or venom. The sense of "virus" as a disease-causing agent came much later, so the Latin root's original meaning of poison is what "virulent" still carries. "Avirulent" inherits that picture in reverse: a pathogen or organism that lacks the poison needed to cause harm.

Synonyms: non-pathogenic, benign

Antonyms: virulent, harmful