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

To manage that reality, Manning encourages newer teachers to establish boundaries early and stick to them. —Tereza Shkurtaj, PEOPLE, 18 Apr. 2026

There’s a see-sawing feeling, Briones adds, between wanting to engage with the fun alongside fans of her work and trying to find a boundary when the attention on the character gets messy or dark. —Jackson McHenry, Vulture, 17 Apr. 2026

However, most existing versions are polycrystalline, which creates resistance at grain boundaries and limits how efficiently ions can move through the material. —Neetika Walter, Interesting Engineering, 17 Apr. 2026

While there was broad cross-party support for increasing women’s representation, opposition parties warned that redrawing voting boundaries and expanding the size of Parliament could shift the political balance in favor of Prime Minister Narendra Modi ’s ruling Bharatiya Janata Party. —ABC News, 17 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