The boundary was originally the landmark, that which marked off one piece of territory from another. Bounds may be used for all within the limits, boundary for the limiting line only.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

limit Brian intends to strictly limit the money he uses.
edge Sami seemed to have the edge on his older brother.
border We met again in Oujda, on the border with Algeria.
barrier There was a language barrier between Ziri and Rima.
separation The separation felt like a never-ending nightmare.
frontier The soldiers headed for the frontier with caution.

Popularity over time

Word	1850 → 2019	Trend
boundary		falling
limit		steady
edge		rising
border		rising
barrier		steady
separation		falling

Use in printed books, per decade from 1850 to 2019.

By length

4 letters: line¹, side¹, term¹, edge¹
5 letters: limit², bound¹, verge¹
6 letters: border²
7 letters: circuit², barrier³
8 letters: frontier²
9 letters: periphery⁴
10 letters: separation⁴
13 letters: circumference³

The small number after each word is its number of syllables (limit² = 2 syllables).

In other languages

Français: limite
Italiano: limite
Español: frontera
Deutsch: Begrenzung
Català: límit