irregular

irregular — adjective

1. An irregular word does not follow the standard patterns that most words of its t

1.adjectiveB1
Definition

An irregular word does not follow the standard patterns that most words of its type follow when changing form — for example, a verb that does not add '-ed' for the past tense, or a noun that does not add '-s' for the plural.

Example

The verb 'go' is irregular because its past tense is 'went', not 'goed'.

irregular verb: past tense not formed with -ed

Children often struggle with irregular plurals like 'mice' and 'children'.

irregular plural: no -s ending

Common collocations
  • irregular verb
  • irregular plural
  • irregular form
  • irregular noun
  • irregular adjective
Synonyms
  • non-standard

    broader; applies to any deviation from a norm, not just grammar

  • exceptional

    more positive; suggests rarity rather than rule-breaking

  • abnormal

    stronger; implies something is wrong, not just different in form

Antonyms
  • regular

    follows the standard inflection pattern

  • standard

    conforming to the usual rules

Grammar Patterns

irregular + noun (verb/noun/adjective)

Usage Note

Only applies to the grammatical behaviour of words. Do not use this sense to describe situations, objects, or people — those belong to the BEHAVIOUR or SHAPE senses.

Common Mistakes

This plan looks irregular' (when meaning suspicious).
This plan looks unusual.
Use the BEHAVIOUR sense (adj/2) for situations, not the GRAMMAR sense.

2. not following the accepted or expected way of doing things — used to describe ac

2.adjectiveB2
Definition

not following the accepted or expected way of doing things — used to describe actions, procedures, or conduct that go against normal rules or customs, often in a way that seems wrong or suspicious.

Example

The company's hiring process was highly irregular — they interviewed nobody in person.

highly irregular — common intensifier pattern

Adina found it irregular that the committee reached a decision without any discussion.

find it irregular + that-clause

Common collocations
  • highly irregular
  • irregular behaviour
  • irregular practice
  • irregular procedure
  • irregular conduct
Synonyms
  • unconventional

    less negative; suggests creativity or independence

  • improper

    stronger moral judgment; implies something is wrong

  • unorthodox

    suggests deviation from established tradition or doctrine

Antonyms

Grammar Patterns

irregular + noun (behaviour/practice/procedure)

it is irregular + to-infinitive

find something + irregular

Usage Note

Often carries a negative or suspicious connotation — stronger than 'unusual'. Commonly found in formal, legal, or professional contexts. Does NOT apply to physical appearance (use SHAPE sense adj/3) or to grammar (use GRAMMAR sense adj/1).

Common Mistakes

He has an irregular face' (meaning unusual-looking).
His face is unusual / asymmetrical.
The BEHAVIOUR sense applies to actions and procedures, not physical appearance.

3. not having a uniform, even, or symmetrical shape; with parts that differ noticea

3.adjectiveB2
Definition

not having a uniform, even, or symmetrical shape; with parts that differ noticeably in size, form, or arrangement — for example, a surface that is not flat, a shape whose sides are not equal, or an object whose outline is uneven.

Example

The garden wall was made of irregular stones of different sizes and colours.

irregular + stones — natural, non-uniform physical objects

Ryo noticed an irregular dark spot on his left arm and decided to see a doctor.

irregular spot — medical context for unusual marks on skin

Common collocations
  • irregular shape
  • irregular surface
  • irregular pattern
  • irregular outline
  • irregular spot
Synonyms
  • uneven

    more common; focuses on lack of flatness or levelness

  • asymmetrical

    more precise; describes lack of mirror-image balance

  • jagged

    specific to sharp, rough edges or outlines

Antonyms
  • even

    flat and uniform in surface

  • symmetrical

    balanced in shape and form

  • uniform

    consistent in size, shape, or arrangement

Grammar Patterns

irregular + noun (shape/surface/pattern)

irregular in + noun phrase

Usage Note

Common when describing natural objects (rocks, coastlines, leaves), handmade items, blemishes on skin, or flawed manufactured goods. Also used in biology and geography.

Common Mistakes

The meeting schedule is irregular' (when meaning unpredictable).
The bus comes at irregular times.
For timing, use the FREQUENCY sense (adj/4); SHAPE is for physical form only.

4. occurring at uneven intervals in time or with unequal distances between points —

4.adjectiveB2
Definition

occurring at uneven intervals in time or with unequal distances between points — used for events, services, biological rhythms, or spatial arrangements that lack a steady, predictable pattern.

Example

Élise made irregular visits to her hometown, sometimes twice a month and sometimes not for a whole year.

irregular visits — varying intervals between events

The bus service was irregular, with long waits between arrivals during the evening rush hour.

Common collocations
  • irregular intervals
  • irregular basis
  • irregular heartbeat
  • irregular breathing
  • irregular rainfall
Synonyms
  • sporadic

    implies long gaps with rare, scattered occurrences

  • intermittent

    suggests alternating between happening and stopping

  • uneven

    broader; can describe quantity or distribution, not just timing

Antonyms
  • regular

    happening at steady, predictable intervals

  • consistent

    unchanging in pattern or frequency

  • steady

    continuous and even in rhythm or rate

Grammar Patterns

irregular + noun (intervals/visits/heartbeat)

at irregular + noun (intervals/times)

become + irregular

Usage Note

Very common in medical descriptions (heartbeat, breathing, pulse) and in discussions of services, weather, attendance, or any repeated event. Distinguish from the BOWEL sense (adj/5), which is specific to digestion.

Common Mistakes

The watch is irregular' (meaning it tells the wrong time).
The watch is inaccurate / broken.
'Irregular' refers to uneven intervals, not incorrect function.

5. relating to a condition where bowel movements happen less often than is normal f

5.adjectiveB2
Definition

relating to a condition where bowel movements happen less often than is normal for a person — used as a polite or clinical way to describe constipation or irregular digestive patterns.

Example

The patient told the nurse she had been irregular for several weeks and felt uncomfortable.

be + irregular — describing a health condition politely

Eating more fibre and drinking enough water can help if you become irregular.

Common collocations
  • become irregular
  • feel irregular
  • been irregular
  • irregular bowels
Synonyms
Antonyms
  • regular

    having normal bowel movement frequency

Grammar Patterns

be + irregular

become + irregular

feel + irregular

Usage Note

A polite, slightly formal way to describe constipation. Used mainly in medical consultations or when speaking about digestive health with some delicacy. 'Constipated' is more direct and common in everyday speech.

Common Mistakes

I feel irregular today' (as a general complaint about feeling unwell).
I have been irregular lately and my stomach hurts.
This sense is specifically about bowel movements, not general health.

6. belonging to a fighting group that operates outside a country's formal military

6.adjectiveB2
Definition

belonging to a fighting group that operates outside a country's formal military structure — used to describe soldiers, troops, or armed units that are not part of the regular national army.

Example

Irregular troops controlled large areas of the countryside after the government lost control.

irregular troops — standard military collocation

The regular army struggled against irregular fighters who knew the terrain well.

contrast: regular army vs irregular fighters

Common collocations
  • irregular forces
  • irregular troops
  • irregular soldier
  • irregular fighters
  • irregular army
Synonyms
  • guerrilla

    more specific; refers to fighters using small, surprise attacks

  • paramilitary

    organised like a military unit but not part of the official armed forces

  • unofficial

    broader; not specific to military contexts

Antonyms
  • regular

    belonging to the official national army

  • official

    formally recognised by the government

Grammar Patterns

irregular + noun (forces/troops/soldiers/fighters)

Usage Note

Often used before a noun ('irregular forces', 'irregular troops'). The standalone noun form 'irregulars' refers to these fighters but is less common. 'Guerrilla' is a related but narrower term referring to a specific type of irregular fighter using hit-and-run tactics.

Common Mistakes

He joined an irregular group' (meaning any unofficial organisation).
He joined an irregular military unit.
This sense is specific to armed fighters and military contexts, not general unofficial groups.

irregular — noun

Word family

  • irregularly
    adverbB2
  • irregularity
    nounB2
  • regular
    adjectiveA2
  • regularly
    adverbA2
  • regularity
    nounB2

Synonym discussion

Sense: adjective/4

Irregular, sporadic, intermittent, and uneven all describe things that do not happen or appear in a steady, predictable way. Irregular is the broadest term, covering anything that breaks a pattern — from bus schedules to heartbeats. Sporadic adds the idea of happening at scattered, unpredictable moments with long gaps in between (e.g., 'sporadic gunfire'). Intermittent suggests alternating between happening and not happening (e.g., 'intermittent rain throughout the afternoon'). Uneven focuses on imbalance or lack of consistency in distribution rather than timing alone (e.g., 'uneven attendance across the different classes'). Choose irregular for general pattern-breaking, sporadic for rare scattered occurrences, intermittent for on-and-off patterns, and uneven for unbalanced distribution. For example: 'Élise made irregular visits to her hometown, sometimes twice a month and sometimes not for a year.' 'The internet connection was intermittent, cutting out every few minutes during the video call.'

irregular ↗sporadicintermittent ↗uneven ↗

Common collocations

Nouns

Adverbs

Phrases

  • at irregular intervals
  • on an irregular basis

Etymology

LatinFrenchEnglish

Irregular entered English in the 14th century from Old French 'irreguler', which came from Latin 'irregularis' — the prefix 'ir-' (meaning 'not') combined with 'regularis' (meaning 'according to rule, regular'). The word first appeared in English texts in the context of grammar, describing verbs and nouns that did not follow standard inflection patterns. By the 16th century, it had expanded to describe behaviour and conduct that broke accepted rules. The senses relating to physical shape and uneven timing developed in the 17th–18th centuries, while the military use appeared in the late 18th century during discussions of non-standard fighting forces in conflicts around the world.