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

With the moon transiting whimsical Pisces, the boundaries between the physical and spiritual blur, adding an imaginative and almost cinematic layer to the festivities. —Valerie Mesa, PEOPLE, 31 Oct. 2025

These teams combine the boundary-busting power of AI with diverse human expertise to consistently produce breakthrough solutions. —François Candelon, Fortune, 31 Oct. 2025

The 6-foot-4-inch Woolen, who is in the final year of his rookie contract, would provide depth on the boundary and could benefit from a change in scenery. —Evan Massey, MSNBC Newsweek, 31 Oct. 2025

Kika explores a particular collision of collapse and reinvention, observing how financial precarity and pressure can erode personal boundaries and generate unexpected forms of empowerment. —Catherine Bray, Variety, 31 Oct. 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