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 researchers acknowledged that the exact boundaries around the venues have not been set. — James Rainey, Los Angeles Times, 4 Sep. 2026

Instead of chopping an object into billions of tiny digital cubes, the system mathematically embeds the boundaries and material densities into quantum states. — Aman Tripathi, Interesting Engineering, 4 Sep. 2026

Clearing the air around chores, privacy and boundaries will make your space feel like yours again. — Valerie Mesa, PEOPLE, 3 Sep. 2026

The plan said public land boundaries should be better defined and the area needed more parking and signage for public safety. — Lily Knoepp, Charlotte Observer, 3 Sep. 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