How to say "replacement" in Japanese

• 代わりかわりJLPT N4approx.Common
  no-adjectiveThe general word for a substitute: someone or something that takes the place of another. Fits contexts like sending a replacement worker or using one thing in place of another.
  自分じぶんで行いく代かわりに手紙てがみを送おくりました。↗

  Instead of going myself, I sent a letter.
• 更新こうしんCommon
  noun, suru verb, transitive verb, intransitive verbReally means renewal or updating; its 'replacement' sense is replacing old data, records, or content with new versions. Choose it when the replacement is an update — refreshing information rather than swapping objects.
  この冬ふゆは降雪量こうせつりょうの記録きろくを更新こうしんした。↗

  This winter the record for snowfall was broken.
• 入れ替えいれかえCommon
  noun, suru verb, transitive verbReplacement in the concrete sense: taking one thing out and putting another in its place, such as swapping parts, equipment, or team members. Use it for physical replacement rather than abstract substitution.
  もし、システムの完全かんぜんな入れ替いれかえが必要ひつようということになれば、彼かれらは古ふるいシステムで満足まんぞくすることと思おもう。↗

  If it's going to require a total restructuring, I'm sure they will be satisfied with the old system.
• 切り替えきりかえCommon
  nounPrimarily switching or conversion — changing over from one state, mode, or system to another. Its 'replacement' gloss is marginal; for plain replacement this is seldom the word you want.
• 入れ替わりいれかわりCommon
  nounThe noun for a changeover: people or things replacing one another, as in staff turnover or a shifting lineup. Emphasizes the mutual exchange or succession rather than a single act of replacing.
  最近さいきん、社員しゃいんの入れ替いれかわりが激はげしくないですか。↗

  The turnover at my company is really speeding up lately.

Use 「代わり」 for a substitute standing in for something, 「入れ替え」 for physically swapping one thing out for another, 「入れ替わり」 for a changeover or turnover, 更新 for replacing by renewal or updating, and 「切り替え」 mainly for switching rather than replacement.

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

• 代わりかわりsubstitute
• 更新こうしんrenewal
• 入れ替えいれかえreplacement
• 切り替えきりかえexchange
• 入れ替わりいれかわりsubstitution
• 差し替えさしかえreplacement
• 新陳代謝しんちんたいしゃrenewal
• 交換こうかんexchange
• 交代こうたいchange
• 補充ほじゅうreplenishment
• 更迭こうてつchange (of personnel)
• かけがえreplacement
• 置換ちかんsubstitution
• 置き換えおきかえreplacement
• 付け替えつけかえreplacement
• リプレースreplacement
• 補用ほようreplacement
• 後釜あとがまsuccessor
• 廃棄処分はいきしょぶんdisposal
• 形成けいせいrepair (e.g. with plastic surgery)
• 替えかえsubstitute
• 交換品こうかんひんsubstitute