How to say "internal" in Japanese

• 内部ないぶJLPT N1approx.Common
  no-adjectiveThe general word for the inside or interior of something, whether a building, a body, or an organization. Use it when 'internal' simply means 'inner' — matters or structure belonging to the inside.
  この図解ずかいは地球ちきゅうの深ふかい内部ないぶを示しめしている。↗

  The illustration shows the deep interior.
• 内蔵ないぞうCommon
  no-adjective, suru verb, transitive verbCovers 'internal' for a mechanism or feature built into a device — the 'built-in' sense. It is not the general word for the inside of something; think of a function housed within the machine itself.
• 対内たいないCommon
  nounCovers 'internal' in the inward-facing sense: matters of a country or organization directed toward those inside, in contrast with external ones. It fits talk of internal as opposed to external affairs.
• 国内こくないCommon
  no-adjectiveMeans 'within the country' — the word to use when 'internal' really means 'domestic': things that happen or are done inside the country rather than abroad.
  アメリカへ行いくくらいなら、国内こくないにいるほうがましだ。↗

  You might as well stay at home as go to America.
• インCommon
  prenominal modifierThe loanword 'in', usually written in kana alone. It is seldom the word you want for 'internal' — it is really just 'in', and the inside sense is better served by 内部.

Choose 内部 for the inside or interior of a thing or organization, 内蔵 for built-in mechanisms or features, 対内 for inward-facing affairs, 国内 for the domestic, within-the-country sense, and 「イン」 only where the loanword 'in' fits.

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

• 内部ないぶinterior
• 内蔵ないぞうinternal (e.g. mechanism, feature)
• 対内たいないdomestic
• 国内こくないwithin the country
• インターナルinternal
• 内部的ないぶてきinternal
• 国内的こくないてきinternal (to a country)
• 内在的ないざいてきimmanent
• 内面的ないめんてきinner
• 内なるうちなるinner (self, voice, man, etc.)
• インin