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

District boundaries are usually adjusted once a decade after a new census. —Arkansas Online, 12 Dec. 2025

Single Americans name excessive debt, financial instability, and failing to respect boundaries among their top dating red flags. —Gili Malinsky, CNBC, 12 Dec. 2025

While leaders will need to decide which categories of decisions remain human-only, which can be delegated to agents, and which require collaboration between the two, the overall focus should be around setting boundaries for agent behaviors. —François Candelon, Fortune, 12 Dec. 2025

While the 84-year-old still goes out to hunt, his two apprentices largely take the helm in helping reinforce the boundary between the forest and residential areas. —Hanako Montgomery, CNN Money, 11 Dec. 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