变复数时，与单数形态一直
- Aircraft – aircraft
- Barracks – barracks
- Deer – deer
- Gallows – gallows
- Moose – moose
- Salmon – salmon
- Hovercraft – hovercraft
- Spacecraft – spacecraft
- Series – series
- Species – species
- Means – means
- Offspring – offspring
- Deer – deer
- Fish – fish
- Sheep – sheep
- Offspring – offspring
- Trout – trout
- Swine – swine
变复数时，改变单数名词的拼写
复数形式通常是改变单数单词中的元音
- Person – people
- Ox – oxen
- Man – men
- Woman – women
- Caveman – cavemen
- Policeman – policemen
- Child – children
- Tooth – teeth
- Foot – feet
- Goose – geese
- Mouse – mice
- Louse – lice
- Penny – pence
复数形式来自于拉丁语或希腊语
a 结尾变为 -ae, 或直接加s
- Alumna – alumnae
- Formula – formulae/formulas
ex or ix 结尾变 -ices
- Index – indices /indexes
- Matrix – matrices
- Vertex – vertices
- Appendix – appendices
is 结尾变 es
- Axis – axes
- Genesis – geneses
- Nemesis – nemeses
- Crisis – crises
- Testis – testes
um 结尾变 -a, 或加 s
- Addendum – addenda
- Corrigendum – corrigenda
- Datum – data
- Forum – fora/forums
- Medium – media/ mediums
- Memorandum – memoranda/memorandums
- Millennium – millennia
- Ovum – ova
- Spectrum – spectra
us 结尾变 -i 或 -era 或 -ora 或加 -es
- Alumnus – alumni
- Corpus – corpora
- Census – censuses
- Focus – foci
- Genus – genera
- Prospectus – prospectuses
- Radius – radii
- Campus – campuses
- Succubus – succubi
- Stylus – styli
- Syllabus – syllabi/syllabuses
- Viscus – viscera
- Virus – viruses/virii
- Cactus – cactuses/cacti
- Fungus – fungi
- Hippopotamus – hippopotamuses/hippopotami
- Octopus – octopuses
- Terminus – termini/terminuses
- Uterus – uteri/uteruses
us 结尾，变复数是保持不变
- Meatus – meatus/meatuses
- Status – status/statuses
on 结尾变 -a
- Automaton – automata
- Criterion – criteria
- Phenomenon – phenomena
- Polyhedron – polyhedra
as 结尾变 -antes
- Atlas – Atlantes (statues of the Titan); but Atlas – atlases (map collections)
ma 结尾变 -mata
- Stigma – stigmata/stigmas
- Stoma – stomata/stomas
- Schema – schemata/schemas
- Dogma – dogmata/dogmas
- Lemma – lemmata/lemmas
- Anathema – anathemata/anathemas
外来语单词变复数
一些法语外来词变复数时，加 -x:
- Beau – beaux/beaus
- Bureau – bureaux/bureaus
- Tableau – tableaux/tableaus
一些斯拉夫语外来词变复数时，加 -a 或 -i 或直接加 -s:
- Kniazhestvo – kniazhestva/kniazhestvos
- Kobzar – kobzari/kobzars
- Oblast – oblasti/oblasts
一些日语外来词的复数就是单词本身:
- Benshi – benshi
- Otaku – otaku
- Samurai – samurai
其他外来语符合英语变复数规则:
- Canoe – canoes
- Igloo – igloos
- Kangaroo – kangaroos
- Kayak – kayaks
- Kindergarten – kindergartens
- Pizza – pizzas
- Sauna – saunas
- Ninja – ninjas
