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

Tuazon strategized with her team about how to get the images needed of both the search operation and any potential memorial, while also remaining cognizant of boundaries – something that the couple often were not afforded during their short lives. —Dan Heching, CNN Money, 26 Mar. 2026

Other people’s reactions bleed into your own experience; the boundary between self and crowd loosens. —Yook Jihun, Popular Science, 26 Mar. 2026

With social boundaries limiting the ability to film with teenage girls and young women, the film instead draws upon the voices and presence of older women, to address gender realities. —Leo Barraclough, Variety, 26 Mar. 2026

Amazon Kids Tablet Deal The Amazon Fire 7 Kids is built specifically for the youngest users in your house, offering a real tablet experience that stays safely within boundaries. —Juhi Wadia, PC Magazine, 25 Mar. 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