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

Your instincts likely encourage generous choices, while setting a clear price or boundary helps exchanges feel fair across your life. —Tarot.com, Hartford Courant, 17 Apr. 2026

The quota, however, is linked to a controversial separate bill to change voting boundaries, a process that could increase the number of seats in the lower house from 543 to about 850. —ABC News, 16 Apr. 2026

Please feel free to tell me if this is crossing the boundary of our friendship. —Ryan Ermey, CNBC, 16 Apr. 2026

The boundary can be remarkably sharp, creating the surreal visual of a literal wall of water moving across the landscape. —Hanna Wickes, Miami Herald, 16 Apr. 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