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 United States often feels more fractured than fraternal, a search for commonality hard to find in a land of boundaries drawn harder each day. —Dana O’Neil, CNN Money, 13 June 2026

In the western part of Colorado's Arapahoe County, boundaries between municipalities can be a little tricky. —Michael Abeyta, CBS News, 12 June 2026

Give your quick mind a private outlet by journaling feelings about spending, then decide on a simple boundary around a tempting add‑on. —Tarot.com, New York Daily News, 12 June 2026

The boundary between legal and non-legal decision-making begins to dissolve, which is where transformed business impacts society as a whole. —Joseph Andrew, Forbes.com, 12 June 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