Plural form of words ending in -us

In Latin, most second declension masculine nouns ending in -us form their plural in -i. However, some Latin nouns ending in -us are not second declension (cf. Latin grammar). For example, third declension neuter nouns such as opus and corpus have plurals opera and corpora, and fourth declension masculine and feminine nouns such as sinus and tribus have plurals {{lang|la|sinūs}} and {{lang|la|tribūs}}.

Some English words derive from Latin idiosyncratically. For example, bus is a shortened form of omnibus 'for everyone', the ablative (and dative) plural of omnis, and ignoramus is a verb form, 'we do not know'. Syllabus is a Late Latin (16th c.) word, derived from a misreading of the Greek sittybos "table of contents"; since it is not a classical word, some argue that it does not have a classical plural.{{cite web |title=Syllabus |url=https://www.etymonline.com/word/syllabus#etymonline_v_22509 |website=Online Etymological Dictionary |accessdate=21 October 2018}} However, the form syllabi is used and considered acceptable by some sources.{{cite web |title=Which Is The Correct Plural Spelling? (It's a Trick Question) |url=https://www.merriam-webster.com/grammar/tricky-plural-words-explained#:~:text=Syllabuses%20%26%20Syllabi&text=Both%20forms%20of%20the%20plural,you%20if%20you%20use%20syllabi. |website=Merriam-Webster |access-date=26 August 2023}}

The English plural of virus is viruses.A Dictionary of Modern English Usage (1950) H. W. Fowler, Oxford University Press In most speaking communities, this is non-controversial and speakers would not attempt to use the non-standard plural in -i. However, in computer enthusiast circles in the late 20th century and early 21st, the non-standard viri form (sometimes even virii) was well attested, generally in the context of computer viruses.VLAD Magazine, Issues #1, #3, #5, #7 Viri is also found in some nineteenth-century sources.{{cite book |page=48 |url=https://archive.org/stream/homopathictreati00test#page/48 |title=A Homœopathic Treatise on the Diseases of Children |first=Alph[onse] |last=Teste |authorlink=Alphonse Teste |translator-first1=Emma |translator-last1=Côté |year=1854 |publisher=Moore, Anderson, Wilstach & Keys |location=Cincinnati}}{{cite book |page=293 |url=https://archive.org/stream/in.ernet.dli.2015.506658/2015.506658.Diseases-Of#page/n327 |title=A Practical Treatise of Diseases of the Urinary & Generative Organs |first=William |last=Acton |authorlink=William Acton (doctor)|edition=third |year=1860 |publisher=John Churchill |location=London}}

While the number of users employing these non-standard plural forms of virus was always a small percentage of the English-speaking population, the variation was notable because it coincided with the growth of the web, a medium on which users of viri were over-represented. As the distribution of Internet users shifted to be more representative of the population as a whole during the 2000s, the non-standard forms saw decline in usage. A tendency towards prescriptivism in the computer enthusiast community, combined with the growing awareness that viri and virii are not etymologically supported plural forms, also played a part.{{Citation needed|date=March 2012}}

Vīrus in Classical Latin was a mass noun, denoting something uncountable. These pluralize only under special circumstances, and no plural form of the word can be found in contemporary texts.June 1999 issue of ASM News by the American Society for Microbiology

The Latin word vīrus was a neuter noun of the second declension, but neuter second declension nouns ending in -us (rather than -um) are rare enough that inferring rules is difficult. (One rare attested plural, pelage as a plural of pelagus, is borrowed from Greek, so does not give guidance for virus.) Plural neuter nouns of other declensions always end in -a (in the nominative, accusative and vocative).

In Neo-Latin, a plural form is necessary in order to express the modern concept of 'viruses', leading to the following declension:[http://www.interrete.de/latein/nuntiifinarch1.html Nuntii Latini: Finnish Broadcasting Company (Radiophonia Finnica Generalis). Archiv I. 19.5.2000 - 6.12.2002]: "NOVUM VIRUS COMPUTATORIUM
Novum viri computatorii genus nomine Code Red in praesenti in Interreti grassatur, ut nuntiavit institutum SANS, cuius est securitati retis informatici providere. Code Red II, quod per cursum electronicum diffunditur, priore viro acerbius est et, postquam in servitoria penetravit, in systema lacunam facit. Ita fieri potest, ut alia vira eaque etiam periculosiora in machinas computatorias irrepant. Iam vermis Code Red I molestissimus fuit, cum biduo in trecenta milia computatrorum in omni orbe terrarum invasit."[http://de.pons.com/%C3%BCbersetzung?l=dela&q=virus Pons: virus]William T. Stearn: Botanical Latin. History, Grammar, Syntax, Terminology and Vocabulary. David & Charles, third edition, 1983. Quote: "Virus: virus (s.n. II), gen. sing. viri, nom. pl. vira, gen. pl. vīrorum (to be distinguished from virorum, of men)."

Usage of virii within Internet communities has met with some resistance, most notably by Tom Christiansen, a figure in the Perl community, who researched the issue and wrote what eventually became referred to in various online discussions as the authoritative essay on the subject,{{cite web|accessdate=29 December 2010|date=17 December 1999|author=Tom Christiansen|authorlink=|url=http://www.ofb.net/~jlm/virus.html|title=What's the Plural of 'Virus'?|publisher=Rick Moen}} favoring viruses instead of virii. The impetus of this discussion was the potential irony that the use of virii could be construed as a claim of superior knowledge of language when in fact more detailed research finds the native viruses is actually more appropriate. In other words, virii is a hypercorrection.

The form viruses appears in the official Scrabble words list,OSW Official Scrabble Words (1989) Chambers but neither viri nor virii does.

In life sciences, "viruses" generally refers to several distinct strains or species of virus. "Virus" is used in the original way as an uncountable mass noun, e.g. "a vial of virus". Individual, physical particles are called "virions" or "virus particles".

There are three plural forms of octopus: octopuses, octopi, and octopodes. A fourth form octopods is occasionally used by scientists for taxonomic purposes.[https://www.ncbi.nlm.nih.gov/pubmed/?term=octopods PubMed search for octopods]. Retrieved March 18, 2018

Currently, octopuses is the most common form in the UK as well as the US; octopodes is rare, and octopi is often objected to as incorrect.Peters, Pam (2004). The Cambridge Guide to English Usage. Cambridge: Cambridge University Press. {{ISBN|0-521-62181-X}}, p. 388.

The Oxford English Dictionary[https://www.oed.com/dictionary/octopus_n?tab=forms#33758176 Oxford English Dictionary] Retrieved November 2, 2023. lists octopi, octopuses and octopodes (in that order); it labels octopodes "rare", and notes that octopi derives from the mistaken assumption that {{lang|la|octōpūs}} is a second declension Latin noun. (The long "ū" is not used in the 2nd declension.) Rather, it is (Latinized) Ancient Greek, from {{transl|grc|oktṓpous}} ({{lang|grc|ὀκτώπους}}, gender masculine), whose plural is {{transl|grc|oktṓpodes}} ({{lang|grc|ὀκτώποδες}}).

Chambers 21st Century Dictionary[http://www.chambersharrap.co.uk/chambers/features/chref/chref.py/main?title=21st&query=octopus Chambers 21st Century Dictionary]. Retrieved October 19, 2007. and the Compact Oxford Dictionary[https://web.archive.org/web/20080808223533/http://www.askoxford.com/concise_oed/octopus Compact Oxford Dictionary] Retrieved October 19, 2007. list only octopuses, although the latter notes that octopodes is "still occasionally used"; the British National Corpus has 29 instances of octopuses, 11 of octopi and 4 of octopodes.{{cn|date=August 2023}} Merriam-Webster 11th Collegiate Dictionary lists octopuses and octopi, in that order;{{cn|date=August 2023}} Webster's New World College Dictionary lists octopuses, octopi and octopodes (in that order).{{cn|date=August 2023}}

Fowler's Modern English Usage states that "the only acceptable plural in English is octopuses," and that octopi is misconceived and octopodes pedantic.Burchfield, R.W., Fowler's Modern English Usage, Oxford University Press, 539.

The term octopod (plural octopods) is taken from the taxonomic order Octopoda but has no classical equivalent. The collective form octopus is usually reserved for animals consumed as food.

The situation with the word platypus is similar to that of octopus; the word is etymologically Greek despite its Latinized ending, and so pluralizing it as if it were Latin (i.e. as platypi) is sometimes ill-considered. As with octopus, importing Greek morphology into English would have platypodes as the plural, but in practice this form is hardly attested outside of discussions about pluralization. In scientific contexts, biologists often use platypus as both the singular and plural form of the word, in the tradition of sheep or fish, but laypersons and scientists alike often use the simple English plural platypuses. Different dictionaries make different recommendations.

As a word in Botanical Latin (as distinct from Classical Latin), cactus follows standard Latin rules for pluralization and becomes cacti, which has become the prevalent usage in English. Regardless, cactus is popularly used as both singular and plural, and is cited as both singular and plural.Random House Unabridged Dictionary (2006) Cactuses is also an acceptable plural in English.

{{See also|Dog Latin}}

Facetious mock-erudite plurals in -i or even -ii are sometimes found for words ending with a sound (vaguely) similar to -us. Examples are stewardi (supposed plural of stewardess) and Elvi (as a plural for Elvis imitators). The Toyota corporation has determined that their Prius model should have the plural form Prii, even though the Latin word prius has a plural priora, the Lada Priora having prior claim to that name—though the common plural is "Priuses".engadget, [https://www.engadget.com/2011/02/21/toyota-decrees-the-plural-of-prius-is-prii-your-latin-teach/ "Toyota decrees the plural of 'Prius' is 'Prii,' your Latin teacher looks on admonishingly"], Tim Stevens, 21 February 2011[http://automotive.speedtv.com/article/green-toyota-readies-fleets-of-priuses/ "GREEN: Toyota Readies Fleet Of Priuses"], John Voelcker Conversely, Toyota has also said that the plural of their Lexus line is Lexus.jalopnik, [https://jalopnik.com/breaking-minds-and-spirits-everywhere-lexus-says-the-p-1834330863 Breaking Minds and Spirits Everywhere, Lexus Says the Plural of 'Lexus' Is 'Lexus'], Alanis King, 26 April 2019 The Winklevoss twins were famously referred to as "the Winklevi" in The Social Network.Vanity Fair, [http://www.vanityfair.com/business/features/2011/12/winklevosses-201112 "The Code of the Winklevi"], Dana Vachon, December 2011

{{Reflist}}

• {{cite web | accessdate=2 January 2005|url=http://dictionary.reference.com/help/faq/language/g63.html|title=What is the plural of virus?|work=reference.com FAQ }}

{{DEFAULTSORT:Plural Form Of Words Ending In -Us}}

Category:English grammar