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 list recognizes the women reshaping business and philanthropy — the leaders whose achievements in 2026 expanded the boundaries of influence, innovation and impact. — Cnbc.com Staff, CNBC, 29 Sep. 2026

All favor Republicans except in California and Utah, where the new boundaries could help Democrats. — Arkansas Online, 29 Sep. 2026

The team put out Akayleb Evans as the other corner opposite Lee in the boundary when Horn was out. — Alex Zietlow, Charlotte Observer, 28 Sep. 2026

The conversation opened with thoughts about how horror has always been a space where filmmakers can take creative swings, experiment with form and push boundaries to do all kinds of fantastic work. — William Earl, Variety, 28 Sep. 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