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

The Full Moon lights up the delicate secrets of your 8th house, asking you to balance vulnerability with practical boundaries. —Tarot.com, New York Daily News, 3 Jan. 2026

Across four seasons, Brooklyn was part of how the Chaos Theory team pushed the boundaries of storytelling within the Jurassic World universe. —Abbey White, HollywoodReporter, 3 Jan. 2026

Western governments have expressed concern that the deployment of nuclear-capable systems in Belarus blurs longstanding boundaries between conventional and nuclear forces in Eastern Europe, increasing risks of escalation in a region already strained by the war in Ukraine. —Kapil Kajal, Interesting Engineering, 2 Jan. 2026

Throughout 22 seasons of Top Chef, the hosts and judges have been treated to quite the buffet of creative, boundary-pushing dishes. —Karla Walsh, Better Homes & Gardens, 2 Jan. 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