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

• 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

When a client doesn’t just smile but elevates—makes more money, sets stronger boundaries or magnetizes healthier relationships—you’re no longer delivering a program. —Shay Levister, Forbes.com, 7 Aug. 2025

Still, once Venus meets with Saturn and Neptune on Aug. 25 and 26, you are encouraged to set firm boundaries with yourself or a significant other. —Valerie Mesa, People.com, 7 Aug. 2025

Kylie Jenner has stretched the boundaries of summer style to its sartorial extremes. —Anna Cafolla, Vogue, 7 Aug. 2025

But community members like Davis say the program blurs the boundaries of school and church and could lead to bullying or ostracization of students who opt out of the program. —Keely Doll, The Courier-Journal, 7 Aug. 2025

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