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

While widely recognized for writing the generation-defining 1995 film Kids at just 19 years old, Korine has continuously pushed the boundaries of traditional filmmaking, seamlessly crossing into painting, photography, collage, drawing, and virtual environments. —Robert Lang, Deadline, 2 Apr. 2026

Enjoying Ye has gone from defending a great, boundary-pushing pop artist who occasionally says unfortunate things to essentially defending one’s right just to feel nostalgia for him. —Sam Goldner, Pitchfork, 2 Apr. 2026

European oak and natural stone are paired with walls of glass that blur the boundaries between inside and out. —Tori Latham, Robb Report, 2 Apr. 2026

At the same time, old sub-disciplinary boundaries within pyschology itself are now crossed more freely; interdisciplinary teams may work on a common problem using methods that draw on multiple levels of analysis, whether social, cognitive, or biological. —Encyclopedia Britannica, 2 Apr. 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