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

If a co-worker asks for help, clarify a fair boundary, then trade a small favor for a realistic timeline. —Tarot.com, Hartford Courant, 29 May 2026

Homes within high-performing elementary boundaries in Charlotte tend to hold their value better and move faster on the market. —Lauren Jarvis-Gibson, Charlotte Observer, 29 May 2026

Nationwide, efforts by both Republicans and Democrats to redraw congressional district maps ahead of November’s midterm elections are dramatically changing political boundaries. —The Editorial Board, Daily News, 29 May 2026

Residents do not care about jurisdictional boundaries. —Mercury News Editorial Board, Mercury News, 29 May 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