Boundary

noun
Frequency
Medium-High
CEFR Level
B2
Register
Neutral
Domain
Everyday
📄

Definition

1. A line or limit that separates one area from another.
2. A border between countries, properties, or regions.
3. A limit on what is acceptable or allowed.
4. Personal limits on how others can treat you.
5. The edge or extent of something.
✨

Context Alive

After years of letting her family make demands on her time without complaint, she finally learned to set clear boundaries with them, explaining calmly but firmly that she would no longer be available for last-minute babysitting requests or guilt trips about missing every single family gathering.
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Meanings

10 meanings
1 A Line Separating One Area from Another (Noun) — VERY COMMON Common ▼
This is the most basic, physical meaning. A boundary is a line—real or imaginary—that marks where one thing ends and another begins. Property boundaries show where your land stops and your neighbor’s starts. Country boundaries separate nations. City boundaries define where urban areas officially end. Sometimes these lines are marked with fences, walls, or signs; sometimes they’re just invisible lines on maps.
💎 Vivid Example
The dispute between the two farmers started over a boundary line that both claimed ran through different parts of the field, with each insisting that the apple tree producing the best fruit was clearly on their side of the property.
2 Personal Limits on Behavior and Treatment (Noun) — VERY COMMON Common ▼
This psychological meaning has become incredibly common in recent years. Personal boundaries are the limits you set about how others can treat you—what you will and won’t accept. Healthy boundaries protect your mental health and self-respect. People talk about “setting boundaries,” “respecting boundaries,” and “crossing boundaries.” It’s about knowing where you end and others begin, emotionally speaking.
💎 Vivid Example
Her therapist helped her understand that setting boundaries with her overbearing mother wasn’t selfish or cruel, but actually necessary for maintaining a healthy relationship where both of them could feel respected and heard.
3 A Limit on What Is Acceptable or Allowed (Noun) — VERY COMMON Common ▼
Boundaries exist in rules, behavior, and social expectations too. There are boundaries of good taste. Professional boundaries that shouldn’t be crossed. Ethical boundaries that define right from wrong. When someone “pushes boundaries,” they’re testing limits—sometimes creatively, sometimes inappropriately. When someone “crosses a boundary,” they’ve gone too far.
💎 Vivid Example
The comedian was known for pushing boundaries with his controversial jokes, walking a dangerous line between edgy humor and genuinely offensive content that sometimes landed him in trouble with audiences and sponsors alike.
4 The Border Between Countries or Territories (Noun) — COMMON Common ▼
On a larger scale, boundaries are the official lines that separate nations, states, or territories. International boundaries are often heavily guarded. Boundary disputes have caused wars throughout history. Some boundaries follow natural features like rivers or mountains; others are straight lines drawn by politicians on maps.
💎 Vivid Example
The boundary between the two countries had been contested for centuries, with both nations claiming the same mountain pass as historically theirs and neither willing to compromise on territory their ancestors had fought and died for.
5 The Edge or Outer Limit of Something (Noun) — COMMON Common ▼
Boundaries can describe the outer edges of anything—physical spaces, concepts, or fields of study. The boundaries of human knowledge. The boundaries of a playing field. The boundaries of what’s possible. It marks where something stops and the unknown or unreachable begins.
💎 Vivid Example
Scientists are constantly working to expand the boundaries of human understanding, exploring questions about the universe that previous generations couldn’t even have imagined asking, let alone answering.
6 A Scoring Shot in Cricket (Noun — Sports) — SPECIALIZED Common ▼
In cricket, a boundary is when the ball reaches the edge of the playing field—either by rolling along the ground (worth four runs) or flying over without bouncing (worth six runs). Cricket fans cheer loudly when batters hit boundaries, and commentators track how many boundaries are scored in a match.
💎 Vivid Example
The crowd erupted when the young batsman smashed the ball over the rope for a massive boundary, a six that sailed into the stands and brought his team within striking distance of winning the championship match.
7 'Push the Boundaries' — To Challenge Limits or Conventions (Idiomatic) — VERY COMMON Common ▼
When you “push the boundaries,” you challenge existing limits—trying new things, testing what’s possible, or going beyond what’s been done before. Artists push creative boundaries. Scientists push boundaries of knowledge. Athletes push physical boundaries. It’s usually positive—suggesting innovation, courage, and progress.
💎 Vivid Example
The architect made her reputation by constantly pushing the boundaries of what buildings could look like and how they could function, designing structures that critics initially called impossible but which are now celebrated as masterpieces.
8 'Cross a Boundary' — To Go Too Far or Behave Inappropriately (Idiomatic) — VERY COMMON Common ▼
When someone “crosses a boundary,” they’ve done something unacceptable—violated someone’s personal limits, broken rules of appropriate behavior, or gone beyond what’s allowed. It’s usually a warning sign or accusation. A boss who crosses boundaries by asking personal questions. A friend who crosses boundaries by sharing your secrets.
💎 Vivid Example
He crossed a serious boundary when he read his teenage daughter’s diary without permission, destroying the trust between them so completely that it took years of apologies and changed behavior before she would confide in him again.
9 'Without Boundaries' — Limitless or Unrestricted (Idiomatic) — COMMON Common ▼
When something exists “without boundaries,” it has no limits—it’s free, unrestricted, infinite. Love without boundaries. Creativity without boundaries. The internet allows communication without boundaries. It sounds liberating, but sometimes having no boundaries can also be chaotic or dangerous.
💎 Vivid Example
The technology promised a future of communication without boundaries, connecting people across continents instantly, though no one had yet considered how this same freedom would be used to spread misinformation just as quickly as truth.
10 'Know No Boundaries' — To Be Unlimited or Not Respect Limits (Idiomatic) — COMMON Common ▼
When something “knows no boundaries,” it extends everywhere without restriction. Love knows no boundaries. Ambition knows no boundaries. Sometimes this is positive—describing something wonderfully unlimited. Sometimes it’s negative—describing something that should be contained but isn’t, like greed that knows no boundaries.
💎 Vivid Example
Her generosity knew no boundaries, giving away money she didn’t really have to spare, volunteering time she couldn’t afford, and helping strangers in ways that sometimes worried her family who feared she would exhaust herself completely.
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Examples from the Street

“You need to set boundaries with your boss — you can’t work weekends forever.”
You need to establish clear limits about what you will and won’t accept
“He has no sense of boundaries — he just asks the most personal questions.”
He doesn’t understand appropriate limits in social situations
“The research is pushing the boundaries of what’s possible.”
The work is going beyond existing limits and exploring new territory
🧩

Common Patterns

set boundaries → establish clear personal limits
establish/create boundaries → put limits in place
respect someone’s boundaries → honour someone’s limits
cross/overstep boundaries → go beyond acceptable limits
healthy boundaries → appropriate, balanced personal limits
personal/professional boundaries → limits in private life or work
the boundary (between) → the dividing line between areas
national/state/county boundary → official border of a region
within the boundaries (of) → inside the limits of an area
mark/define the boundary → indicate where a limit is
push/expand the boundaries → go beyond current limits
the boundaries of science/knowledge/possibility → the limits of what is known or achievable
blur the boundaries (between) → make distinctions less clear
break down boundaries → remove barriers or divisions
🔗

Collocations

5 collocations
set boundaries
establish limits on what is acceptable
push the boundaries
go beyond existing limits
cross a boundary
go past an accepted limit
personal boundaries
limits on how others can treat you
clear boundaries
well-defined and obvious limits
✍️

Example Sentences

12 examples
1
Learning to set boundaries at work has improved my mental health enormously
Establishing clear limits in my professional life has benefited my psychological wellbeing tremendously.
2
You need to respect her boundaries — if she doesn’t want to talk about it, don’t push
You must honour her personal limits — if she’s unwilling to discuss the matter, don’t pressure her.
3
He crossed a boundary when he started reading my private messages
He went too far when he began looking through my personal communications.
4
Maintaining healthy boundaries in relationships is essential for both partners
Keeping appropriate limits in partnerships is crucial for everyone involved.
5
The river forms a natural boundary between the two countries
The waterway creates a natural dividing line separating the two nations.
6
Scientists continue to push the boundaries of artificial intelligence
Researchers keep going beyond the current limits of machine learning technology.
7
Social media has blurred the boundaries between public and private life
Online platforms have made the distinction between our open and personal existence less clear.
8
The festival aims to break down boundaries between different musical genres
The event seeks to remove barriers separating various styles of music.
9
Some people have no sense of professional boundaries — they share far too much personal information at work
Certain individuals don’t understand appropriate workplace limits — they reveal excessively private details to colleagues.
10
The property boundary is marked by that old stone wall
The edge of the land is indicated by that ancient rock barrier.
🎓 Learner Examples
★
Teachers need to set clear boundaries with students while still being approachable and supportive
Instructors must establish firm limits with learners whilst remaining friendly and helpful.
★
Learning a new language pushes the boundaries of your comfort zone — you have to accept feeling awkward at first
Acquiring a foreign tongue takes you beyond your usual ease — you must tolerate feeling uncomfortable initially.
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Phrasal Verbs & Idioms

2 items
💬 Idioms & Expressions
push the boundaries — go beyond normal limits
The artist is known for pushing the boundaries of modern sculpture.
set boundaries — establish personal limits
It's important to set boundaries between your work and personal life.
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Synonyms & Antonyms

6 items
✅ Synonyms
limit
the edge of what's acceptable
border
a dividing line
line
informal, a point you don't cross
edge
the outer point
❌ Antonyms
freedom
no restrictions
openness
no barriers