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

The drive benefits the 4 Community Care food pantry that serves seniors and families living within the Poway Unified School District boundaries dealing with food insecurity. —Pomerado News, San Diego Union-Tribune, 27 Feb. 2026

Over time, the system has grown more precise—expanding from four seasons into 16 nuanced subcategories, allowing for a more personalized understanding of color and how palettes can subtly bridge between seasonal boundaries. —Conçetta Ciarlo, Vogue, 26 Feb. 2026

That said, the empath’s best friend is having stringent boundaries. —Magi Helena, Dallas Morning News, 26 Feb. 2026

The series centers on a couple whose lives are upended after welcoming a seemingly ideal caregiver into their home, only to find boundaries blurred and control slipping as the arrangement spirals into a tense, unsettling power struggle. —Peter White, Deadline, 26 Feb. 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