What are Plurals?
A plural noun indicates more than one of something. Most English plurals are formed by adding -s or -es to the base noun (cat/cats, bus/buses). However, a significant number of high-frequency nouns have irregular plurals (child/children, man/men, foot/feet) that must be learned individually — there is no rule that predicts them.
English also borrows plural forms from other languages, particularly Latin and Greek. These academic and scientific plurals (criterion/criteria, phenomenon/phenomena, datum/data) appear frequently in formal and academic writing and are commonly pluralised incorrectly. At B1 level, using 'criterias' or 'phenomenons' signals a gap in academic vocabulary.
Some nouns have the same form in singular and plural (sheep, deer, fish, series, species). Other nouns appear only in plural form even when referring to a single object (trousers, scissors, glasses). These are conventionally called 'pluralia tantum' and take plural verbs even in singular referential meaning.
Plural Formation Rules
Apply the rules in order: check for an irregular plural first, then apply the spelling rule that matches the noun's ending.
Plural = base noun + -s (regular) OR irregular form (must be learned)Regular Plurals
| Noun ending | Plural rule | Examples |
|---|---|---|
| most nouns | add -s | cat/cats, table/tables, report/reports |
| -s, -ss, -x, -z, -ch, -sh | add -es | bus/buses, class/classes, box/boxes, church/churches, dish/dishes |
| consonant + -y | change -y to -ies | city/cities, country/countries, policy/policies |
| vowel + -y | add -s (no change) | day/days, key/keys, survey/surveys |
| most nouns ending in -o | add -s or -es (both common) | photo/photos, piano/pianos, potato/potatoes, tomato/tomatoes |
| most nouns ending in -f or -fe | change -f/-fe to -ves | leaf/leaves, life/lives, wife/wives, half/halves |
| exceptions: -f endings that just add -s | add -s | roof/roofs, chief/chiefs, chef/chefs, cliff/cliffs |
Irregular Plurals
| Singular | Plural | Note |
|---|---|---|
| man | men | also: woman/women |
| child | children | not 'childs' or 'childrens' |
| tooth | teeth | also: foot/feet, goose/geese, mouse/mice, louse/lice |
| person | people (general) / persons (formal/legal) | 'persons' used in official or legal contexts |
| ox | oxen | rare irregular -en plural |
Latin and Greek Plurals
| Singular | Plural | Common in |
|---|---|---|
| criterion | criteria | academic writing, research, standards |
| phenomenon | phenomena | science, philosophy, journalism |
| datum | data | research, statistics (note: 'data' is now often used as uncountable) |
| medium | media | communications, arts (but 'mediums' for spiritualists) |
| stimulus | stimuli | psychology, biology, economics |
| alumnus | alumni | education (alumna/alumnae for feminine forms) |
| analysis | analyses | also: thesis/theses, hypothesis/hypotheses, basis/bases |
| appendix | appendices (or appendixes) | 'appendices' in academic / 'appendixes' in medical |
Zero-change and Pluralia Tantum
| Type | Examples | Grammar |
|---|---|---|
| Same in singular and plural | sheep, deer, fish (also fishes), species, series, aircraft | one sheep / three sheep — no change |
| Always plural (pluralia tantum) | trousers, scissors, glasses, headphones, tongs, pliers | take a plural verb: 'The scissors are sharp.' |
| Collective nouns (British English) | the team are / the government have / the staff are | British English treats collective nouns as plural |
Key Plural Contexts
Latin and Greek plurals in academic writing
Latin and Greek plurals are common in academic, scientific, and formal professional writing. Using the anglicised plural ('criterions', 'phenomenons') marks the writer as unfamiliar with the vocabulary of the field. Learn the most common irregular forms.
- The selection criteria were clearly stated in the methodology. (criterion → criteria)
- Several phenomena remain unexplained by current theory. (phenomenon → phenomena)
- The data suggest a strong correlation. (datum → data — plural verb in academic writing)
- The analyses were conducted independently. (analysis → analyses)
Collective nouns — British vs American agreement
Collective nouns (team, committee, government, staff, board) refer to a group of individuals. British English treats them as grammatically plural; American English treats them as singular. Choose one convention and be consistent.
- British: The committee have reached a decision. / The team are preparing.
- American: The committee has reached a decision. / The team is preparing.
- Both correct — just different conventions.
Plural Warning Signals
Regular vs Irregular Plural
Regular plurals follow predictable rules. Irregular plurals do not — the form must be memorised. The most common irregular plurals appear constantly in IELTS and academic writing.
Regular plural — add -s or -es
The researchers submitted their reports on three topics.
reports, topics — standard -s plural.
Irregular plural — memorise the form
The criteria for all three analyses were the same.
criteria (not criterias) and analyses (not analysises) — Latin and Greek plurals.
Common Mistakes
Using 'criterias' or 'phenomenons'
✗ The criterias for selection were not clearly defined. Two phenomenons were observed.
The criteria for selection were not clearly defined. Two phenomena were observed.
'Criteria' and 'phenomena' are already plurals — 'criterion' and 'phenomenon' are the singulars. Adding -s to a Latin/Greek plural is a double-plural error.
Wrong plural for nouns ending in consonant + -y
✗ Several countrys reported an increase. The new policys were unpopular.
Several countries reported an increase. The new policies were unpopular.
When a noun ends in consonant + -y, change the -y to -ies. Vowel + -y just adds -s: day/days, survey/surveys.
Writing 'peoples' for the general plural of 'person'
✗ Many peoples attended the event.
Many people attended the event.
'People' is already the standard plural of 'person'. 'Peoples' means distinct ethnic or national groups: 'the peoples of Central Asia'.
Treating 'data' as singular in academic writing
✗ The data shows a clear trend. (in an academic paper)
The data show a clear trend. (academic) / The data shows a clear trend. (general/informal)
In academic writing following APA, Chicago, or Oxford style, 'data' is the plural of 'datum' and takes a plural verb. Using singular 'data is' in a research paper can be marked as an error.
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