# boundary

/ˈbaʊndɝi/ (US) · /bˈaʊndəɹi/ (UK)

Source: https://englishreference.com/word/boundary
Updated: 2026-06-19

## Senses

### 1. physical border

noun · CEFR B1

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

For teachers: 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.

### 2. social or personal limit

noun · CEFR B2

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

For teachers: 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.

### 3. sporting edge

noun · CEFR C1 · British English

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

For teachers: 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.

### 4. mathematical limit

noun · CEFR C2 · Technical

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

For teachers: 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.

## Examples

- The fence marks the boundary between the two gardens.
- Setting a clear boundary between work and home life is essential for maintaining your mental health.
- The treaty established a new international boundary along the river, though local communities continued to cross the water as they had for centuries before the formal agreement.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.