English Reference

Word

boundary

Phoneticsbound·ary

US/ˈbaʊndɝi/

UK/bˈaʊndəɹi/

Definitions

01physical border

B1 · Intermediate Countable noun

n. a real or imagined line that marks the edge of a place, like a country or a garden.

n. a line or border marking the limit of a physical area or territory.

“The river forms a natural boundary between the two farms.”

“The surveyors spent weeks marking the exact boundary between the private estate and the newly designated national park.”

Antonyms

02social or personal limit

B2 · Upper Intermediate Countable noun

n. a limit that you set to protect your feelings, privacy, or time.

n. a metaphorical limit or rule defining acceptable behaviour, privacy, or professional conduct in social interactions.

“It is important to set clear boundaries between your work life and your home life.”

“The therapist emphasized the importance of maintaining professional boundaries when dealing with long-term clients to ensure objective care.”

03sporting edge

C1 · Advanced Countable noun Sports British English

n. the edge of the playing area in a game like cricket.

n. the outer limit of a playing field, or a scoring event where the ball crosses this line.

“The batsman hit the ball hard and it flew over the boundary for six runs.”

“The fielder made a desperate dive to stop the ball before it reached the boundary, but his effort was just a second too late.”

Usage

often used in the context of cricket to describe a hit that scores four or six runs.

04mathematical limit

C2 · Proficiency Countable noun Mathematics Technical

n. the set of points on the very edge of a shape or group of numbers.

n. the set of points in the closure of a set that do not belong to its interior.

“The boundary of the circle is the line that forms its circumference.”

“In topology, the boundary of a set is defined as the intersection of the closure of the set and the closure of its complement.”

Synonyms

Antonyms

Collocations

Common phrases and expressions where native English speakers use the word “boundary” in context.

Verb

01. cross boundary

“The artist's work tends to cross the boundary between sculpture and performance art.”

verb + noun

02. define pattern boundary

“Researchers use algorithms to define the pattern boundary within the complex data set.”

verb + noun

Noun

03. boundary blur

“As remote work becomes common, the professional and personal boundary blurs significantly.”

noun + verb

04. spectrum boundary

“The device operates at the very edge of the visible light spectrum boundary.”

noun + noun

05. perspective boundary

06. range boundary

07. term boundary

08. view boundary

Real-World Examples

“For decades, India has refused to recognise a Pakistan-China boundary in a disputed part of the Himalayas that Delhi claims as its own.”
BBC 20 Sept 2026
“I respect Austen’s skill, but I’m drawn to books about characters who cross boundaries, venture into the unknown rather than finding their place within the social order.”
The Guardian 31 Jul 2026
“The Richmond Boundary Walk, which traces its origins back to 1576, invites local residents, under the guidance of the town's mayor, to traverse the perimeter of the town every seven years.”
BBC 28 Aug 2025
“But it doesn’t feel confrontational; more demarcating well-defined boundaries and a hard-won ability to claim their achievements.”
The Guardian 14 Aug 2026

Etymology

From bound + -ary, Old French, from Latin.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Synonyms

Antonyms

Word family

NOUN

boundary(C1)

ADJECTIVE

Related words

This entry

Exam level
CambridgeCambridgeCambridge English QualificationsThe exam suite from Cambridge University Press & Assessment, from A1 Movers up to C2 Proficiency. The benchmark names double as CEFR labels.C1 AdvancedIELTSIELTSInternational English Language Testing SystemThe 0–9 band test co-owned by the British Council, IDP, and Cambridge. Used for university entry, work, and migration.7.0–8.0TOEFL iBTTOEFL iBTTest of English as a Foreign Language, Internet-Based TestETS's academic English test, the standard route for US university admissions. Scored 0–120, with a 1–6 scale since 2026.1–6 scale: 5.0–5.595–113TOEICTOEICTest of English for International CommunicationETS's workplace English test, big in Japan and Korea. Listening & Reading scores 10–990 and tops out at C1.945–990
Frequency
Common
Level
C1 · AdvancedOxford
Updated

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