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

Libra September 23 – October 22 Set healthy boundaries in relationships today. — Tarot.com, Chicago Tribune, 21 Aug. 2026

That's because the boundary between internal and external communications is far more permeable than many organizations realize. — Caroline Johns, Forbes.com, 21 Aug. 2026

CRAs are redevelopment districts funded by property taxes collected within their boundaries to pay for real estate projects, road repair, events and other local benefits. — Douglas Hanks, Miami Herald, 21 Aug. 2026

Chef Roy Choi, one of the founders of the food-truck movement, says his Kogi BBQ business could only have started in Los Angeles, a city where food boundaries don’t exist and street culture brings people together. — Dinah Eng, Los Angeles Times, 21 Aug. 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