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

Leaders who pay attention to these lessons now will be best prepared to thrive in a world where the boundaries between Earth and orbit are becoming ever thinner. —Bernard Marr, Forbes.com, 12 Sep. 2025

Kristen Harrison, Richard Cole Eminent Professor at the UNC Hussman School of Journalism and Media, suggested turning off notifications on social media and news apps can help you to set boundaries with the news cycle. —Charles Trepany, USA Today, 12 Sep. 2025

The rain is much needed, as most of the Kansas City forecast area is abnormally dry, with moderate drought conditions creeping closer to its boundaries in mid-Missouri, the weather service said. —Robert A. Cronkleton, Kansas City Star, 12 Sep. 2025

Further, our study shows that entrepreneurs who set work-life boundaries for themselves experience less burnout. —Samantha Dewalt, Fortune, 12 Sep. 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