How to say "boundary" in Japanese

• 境界きょうかいJLPT N2approx.Common
  nounThe most direct equivalent: a line or limit separating two areas, from land and national borders to abstract limits between domains. For most senses of 'boundary' this is the word you want.
  彼かれらは境界きょうかいを越こえてスペインに入はいった。↗

  They crossed the border into Spain.
• 境さかいJLPT N3approx.Common
  nounAlso means a border or boundary, but as a standalone word it leans literary, marking the dividing line between lands, states, or realms; for an ordinary boundary line, 境界 is usually the better choice.
  彼かれは生死せいしの境さかいをさ迷まよった。↗

  He hovered between life and death.
• 境目さかいめCommon
  nounThe line or spot where one thing ends and the next begins, used both concretely (where two colors meet) and figuratively (the borderline between childhood and adulthood); more concrete in feel than 境界.
• ボーダーCommon
  nounA loanword for 'border' or 'boundary', typically for crossing a border or for a cutoff line; in fashion contexts it means stripes, so it is no general substitute for 境界.
• 仕切りしきりCommon
  nounA physical divider: the partition between rooms, the compartments of a box, or, figuratively, the division separating groups. Choose it when 'boundary' means a dividing structure or barrier rather than an abstract line.
  ホールは仕切しきりを設もうける前まえは千せん人にん収容しゅうようできた。↗

  The hall could seat a thousand people before it was partitioned.

Use 境界 for a boundary line or limit between areas or domains, 境目 for the concrete spot where things divide, 「仕切り」 for a physical partition, and treat 境 and 「ボーダー」 as narrower, special-purpose options.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 境界きょうかいboundary
• 境さかいborder
• 境目さかいめborderline
• ボーダーborder
• 仕切りしきりpartition
• 臨界りんかいboundary
• 枠外わくがい(beyond the) limits
• 区域くいきarea
• 区画くかくdivision
• バウンダリーboundary
• 境域きょういきboundary
• 地界ちかいboundary
• 見切り線みきりせんboundary
• 筆界ひつかいboundary (e.g. of property)
• 地境じざかいland border
• 際涯さいがいlimits
• 一線いっせんboundary
• 見切りみきりedge (e.g. of an architectural member)
• けじめboundary
• 界かいborder