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

Koltai asks visitors to communicate their expectations and boundaries, but acknowledges that people can feel violated and that staff aren’t always present or equipped to monitor encounters. — Alison Foreman, IndieWire, 5 Oct. 2026

The race will take place under new boundaries approved through Proposition 50, which shifted the district west to include McGuire’s Democrat-leaning political stronghold of Santa Rosa and other parts of Sonoma County. — Mathew Miranda, Sacbee.com, 5 Oct. 2026

The objective is deliberate autonomy, with clear decision rights, boundaries and escalation paths. — Rahul Saluja, Forbes.com, 5 Oct. 2026

Eagle Creek, one of the forest’s six roadless areas, sits near southern Illinois landscapes with a long history of coal mining, including active and historic mining areas outside the Shawnee’s boundaries. — Christiana Freitag, Chicago Tribune, 4 Oct. 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