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

Breaking this loop requires proactive measures like setting boundaries and taking microbreaks throughout the day. — Mena Mirhom, Forbes.com, 1 Aug. 2026

Workers welded and inspected every pipe joint to guarantee a pressure-tight boundary. — Aman Tripathi, Interesting Engineering, 31 July 2026

The single-story structure revolves around a soaring central living and dining pavilion where floor-to-ceiling glass dissolves the boundary between indoors and out. — Abby Montanez, Robb Report, 30 July 2026

Lal Ded’s poetry also emphasized that the search for the divine transcends religious boundaries. — Peter Dziedzic, The Conversation, 30 July 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