Virus

The word virus is derived from the Latin virus, meaning roughly "poison" or "venom", and still retains this meaning.

• In biology, virus refers to parasitic agents that are smaller than bacteria and that can only reproduce after infecting a host cell; see virus (biology).
• In computer science, a virus is a (usually malicious) computer program that can travel surreptitiously from computer to computer; see computer virus.
• Virus is also used metaphorically to refer to other entities, such as ideas, that can spread rapidly by "infecting" their hosts (see also meme). Certain types of software licence have been called "viral" because they require that derivative works be released under the same licence, GPL being a prominent example.
• Virus is the title of no fewer than 5 feature films:
  • Virus (2002 movie)
  • Virus (2001 movie)
  • Virus (1999 movie)
  • Virus (1995 movie)
  • Virus (1981 movie)

Plural form

There is some controversy about the plural form of 'virus' in English.

One position is that 'viruses' is the correct plural; this view can be justified on these grounds:

• Wikipedia (see English plural) and most English language dictionaries give the plural of 'virus' simply as 'viruses'.¹
• in English, the plural is normally formed by adding -s or -es, but sometimes the plural form in the language of origin is permissible or even preferred;
• in Latin, virii is not the correct plural because the "ii" ending is only used to form the plural of words ending in "ius".
• in Latin, 'viri' is not the correct plural because the "i" plural ending is only used for masculine nouns, and in any case, "viri" is Latin for "men"
• there is no extant record of 'virus' being used in Latin in a plural form, and it is unclear how a plural might have been formed had the word acquired a meaning requiring a plural form.²

Another position is that 'virii' can also be justified because:

• the spelling virii is linked to a specific technical field (computer science), and so is considered jargon.
• the term is an English language term, not Latin.

In any case, the spelling 'virii' is a jargonized modern usage deriving from the English word 'virus' in reference to computer virus.

Footnotes

1. The same is true of specialized dictionaries, e.g.:

• Free On-line Dictionary of Computing entry on virus
• The On-line Medical Dictionary entry on virus

See also the detailed analysis on the Perl programming language web site: What's the Plural of `Virus'? 2. There is some debate about what the rules of Latin grammar might imply about the formation of a plural. In Latin virus is generally regarded to be a neuter of the second declension, a form so rare that there are no recorded plurals, and so there is no classical rule for forming its plural. Possibilities include "virus" (in analog with 4th declension) and "vira" (in analog with 3rd declension).