Level: A2-B1
Irregular English Nouns
Common irregular countable nouns, each shown with its singular and irregular plural form plus a short definition.
- People & Family
- alumna, alumnae – a woman who has graduated from a school or university
- alumnus, alumni – a person who has finished school or university
- brother, brethren – members of the same religious group (rare; formal or religious use)
- child, children – a young person below adulthood
- fireman, firemen – a person who fights fires (now usually called “firefighter”)
- life, lives – the condition of being alive
- man, men – an adult male human
- person, people – one individual; more than one individual
- thief, thieves – someone who steals things
- wife, wives – a married woman
- woman, women – an adult female human
- Body Parts
- calf, calves – the lower back part of your leg (or a young cow)
- foot, feet – the part you stand on at the end of your leg
- knife, knives – a sharp tool for cutting
- self, selves – your own person or persons
- tooth, teeth – the hard things in your mouth used for biting
- Animals & Nature
- cactus, cacti – a plant that grows in the desert
- deer, deer – a wild animal with antlers
- fish, fish – an animal that lives and swims in water
- focus, foci – the center point of attention or activity
- fungus, fungi – a living thing like a mushroom or mold
- goose, geese – a large water bird with a long neck
- hero, heroes – a person admired for bravery or good acts
- leaf, leaves – the flat, green part of a plant
- loaf, loaves – a single piece of baked bread
- louse, lice – a tiny insect that lives on people or animals
- mosquito, mosquitoes – a small insect that bites people and animals
- mouse, mice – a small animal with a long tail
- ox, oxen – a strong animal used on farms
- radius, radii – a straight line from the center of a circle to the edge
- sheep, sheep – a farm animal with wool
- species, species – a group of living things that are similar
- stimulus, stimuli – something that causes a reaction
- wolf, wolves – a wild animal similar to a dog
- Objects, School & Science
- analysis, analyses – detailed study of something
- appendix, appendices – extra information at the end of a book
- axis, axes – a line around which something turns or rotates
- basis, bases – the main reason or starting point for something
- criterion, criteria – a standard or rule for making a judgment
- crisis, crises – a time of serious trouble or danger
- curriculum, curricula – the subjects studied in a school or course
- datum, data – a single fact; information (plural: data)
- diagnosis, diagnoses – a doctor’s finding about an illness
- formula, formulae – a math or science rule using symbols (formulas also used)
- genus, genera – a group of related species in science
- index, indices – a list to help you find things in a book (indexes is also correct)
- matrix, matrices – something in which things form or grow; a grid of numbers
- medium, media – a way to communicate or send information (mediums for “spiritualists”)
- memorandum, memoranda – a written message or note for business
- parenthesis, parentheses – curved marks ( ) used in writing
- phenomenon, phenomena – an event or fact that can be seen or studied
- syllabus, syllabi – a summary or outline of a course (syllabuses also correct)
- thesis, theses – a long research paper or essay
- vertex, vertices – the highest point or a corner in shapes
- Miscellaneous
- aircraft, aircraft – a vehicle that flies
- crossroads, crossroads – a place where two or more roads meet
- echo, echoes – a sound that bounces back and repeats
- embargo, embargoes – a ban on trade with another country
- emphasis, emphases – special importance or focus
- headquarters, headquarters – the main office or center
- means, means – a way or method to do something
- offspring, offspring – a child or animal’s young
- series, series – a group of related things in order
- torpedo, torpedoes – an underwater weapon
- veto, vetoes – the power or act to stop a decision