boundary

noun

bound·​ary ˈbau̇n-d(ə-)rē 

plural boundaries

: something that indicates or fixes a limit or extent

Those two trees mark the boundary of our property.

the mountain range that forms the country's northern boundary

boundaryless

ˈbau̇n-d(ə-)rē-ləs 

adjective

boundarylessness noun

Synonyms of boundary

• limit
• limitation
• confines
• line

Examples of boundary in a Sentence

Those two trees mark the boundary of our property.

The river forms the country's western boundary.

at the boundary between fact and fiction

You need to set boundaries with your children.

Did he violate the boundaries of the doctor-patient relationship?

Recent Examples on the Web

This entrenched cross-border militant networks and blurred the boundary between state policy and nonstate actors, resulting in dynamics that continue to shape the region. —Rabia Akhtar, The Conversation, 20 Mar. 2026

Moving from one house to another caring for the elderly, rarely stopping to rest, Selvi begins to confront the weight of guilt, love and survival as long hours blur the boundaries between care and exhaustion. —Naman Ramachandran, Variety, 19 Mar. 2026

Paxton’s office is contesting the district’s boundaries and wants the land tied to The Meadow development removed. —Nick Wooten, Dallas Morning News, 19 Mar. 2026

Delivery tasks are distributed among everyone who is online, and there’s no sharp boundary between having a job and not having one. —Andrew Garin, Fortune, 19 Mar. 2026

Word History

Etymology

bound entry 6 + -ary entry 1

First Known Use

1598, in the meaning defined above

Phrases Containing boundary

• boundary layer
• K-T boundary

Kids Definition

boundary

noun

bound·​ary ˈbau̇n-d(ə-)rē 

plural boundaries

: something that points out or shows a limit or end : dividing line

Legal Definition

boundary

noun

bound·​ary

plural boundaries

: a theoretical line that marks the limit of an area of land