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

Coca-Cola and the automobile predate it, and its boundaries have repeatedly been contested and rewritten. — Manvir Singh, New Yorker, 2 Nov. 2026

Thermodynamic limit to reduce voltage losses The team discovered a thermodynamic boundary for photocurrent generation and found that using more rigid donor molecules could reduce radiative voltage losses. — Muskan Bhatia, Interesting Engineering, 2 Nov. 2026

There’s also the question of whether people will rely on AI too much, and how to draw boundaries when figuring out which tasks to outsource to AI. — Lisa Eadicicco, CNN Money, 2 Nov. 2026

If an exact wetland boundary is needed, the applicant may also be required to provide a field wetland delineation prepared by a soil scientist. — Dr. Avishesh Neupane, Hartford Courant, 1 Nov. 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