The 100 Most Common Irregular Plural Nouns in English

Most English nouns form their plural by adding either -s (books, bands, bells) or -es (boxes, bunches, batches). These plural forms are said to follow a regular pattern. Irregular Plural Nouns The Penguin Writers Manual There are no easy rules, unfortunately, for irregular plurals in English. They simply have to be learnt and remembered. Not all nouns conform to the standard pattern. In fact, some of the most common English nouns have irregular  plural forms, such as woman/women and child/children. In addition, several nouns have alternative plurals, one regular and the other irregular. In regard to these alternative forms, there are no strict rules to guide our use of them. The Cambridge Encyclopedia of the English Language People have to learn which form to use as they meet the words for the first time, and must become aware of variations in usage. When there is a choice, the classical [irregular] plural is usually the more technical, learned, or formal, as in the case of formulas vs. formulae or curriculums vs. curricula. Sometimes, alternative plurals have even developed different senses, as in the cases of (spirit) mediums vs.  (mass) media, or appendixes (in bodies or books) vs. appendices (only in books). As youll see in the list that follows, many words with irregular plurals are loanwords that have kept their foreign plural forms (or at least held on to those forms as alternatives to regular English plurals). 100 Irregular Plural Nouns List In the list below, youll find singular noun forms in the left column and the corresponding plural forms in the right column. When a noun has more than one plural form, the irregular one appears first, though that doesnt necessarily mean that the irregular form is more widely accepted than the regular form. addendum addenda or addendums aircraft aircraft alumna alumnae alumnus alumni analysis analyses antenna antennae or antennas antithesis antitheses apex apices or apexes appendix appendices or appendixes axis axes bacillus bacilli bacterium bacteria basis bases beau beaux or beaus bison bison bureau bureaux or bureaus cactus cacti or cactus or cactuses chteau chteaux or chteaus child children codex codices concerto concerti or concertos corpus corpora crisis crises criterion criteria or criterions curriculum curricula or curriculums datum data deer deer or deers diagnosis diagnoses die dice or dies dwarf dwarves or dwarfs ellipsis ellipses erratum errata faux pas faux pas fez fezzes or fezes fish fish or fishes focus foci or focuses foot feet or foot formula formulae or formulas fungus fungi or funguses genus genera or genuses goose geese graffito graffiti grouse grouse or grouses half halves hoof hooves or hoofs hypothesis hypotheses index indices or indexes larva larvae or larvas libretto libretti or librettos loaf loaves locus loci louse lice man men matrix matrices or matrixes medium media or mediums memorandum memoranda or memorandums minutia minutiae moose moose mouse mice nebula nebulae or nebulas nucleus nuclei or nucleuses oasis oases offspring offspring or offsprings opus opera or opuses ovum ova ox oxen or ox parenthesis parentheses phenomenon phenomena or phenomenons phylum phyla quiz quizzes radius radii or radiuses referendum referenda or referendums salmon salmon or salmons scarf scarves or scarfs self selves series series sheep sheep shrimp shrimp or shrimps species species stimulus stimuli stratum strata swine swine syllabus syllabi or syllabuses symposium symposia or symposiums synopsis synopses tableau tableaux or tableaus thesis theses thief thieves tooth teeth trout trout or trouts tuna tuna or tunas vertebra vertebrae or vertebras vertex vertices or vertexes vita vitae vortex vortices or vortexes wharf wharves or wharfs wife wives wolf wolves woman women Sources Crystal, David. The Cambridge Encyclopedia of the English Language. 3rd Edition, Cambridge University Press, January 24, 2019.Manser, Martin. Penguin Writers Manual. Penguin Reference Books, Stephen Curtis, Paperback, International Edition, UK ed. edition, Penguin UK, August 24, 2004.