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

Missouri voters will also decide in November whether to use the new GOP-friendly congressional boundaries in 2028 and beyond. — Matthew Kelly, Kansas City Star, 11 Sep. 2026

Its collection deliberately defies conventional boundaries between fine and popular art, placing painting and sculpture alongside illustration, comics, photography, and cinema. — Encyclopedia Britannica, 11 Sep. 2026

At this temperature, as per the researchers, the film sits at the boundary between behaving as a superconductor with no electrical resistance, and an ordinary metal with measurable resistance. — Georgina Jedikovska, Interesting Engineering, 11 Sep. 2026

The state court had found that voters should first have an opportunity to vote on the new district boundaries in a statewide referendum. — Arkansas Online, 10 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