How to say "lethal" in Japanese

• 致死ちしCommon
  no-adjectiveA noun for lethality, the property of causing death. It is the word behind scientific and medical uses of 'lethal', such as 'lethal dose', rather than the adjective for calling something deadly.
• 致命的ちめいてきCommon
  na-adjectiveThe adjective for 'fatal; lethal': wounds, mistakes, or flaws so serious that they prove deadly or decisive. Use this when you want to say, in an ordinary sentence, that something is lethal or fatal.
  そのスキャンダルは彼かれの政治的せいじてき将来しょうらいに致命的ちめいてきであった。↗

  The scandal was fatal to his political future.

Choose 致命的 when 'lethal' works as an adjective describing something deadly or disastrous; 致死 is the noun for lethality itself, typical of scientific and medical expressions, so the two are not interchangeable.

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

• 致死ちしlethal
• 致命的ちめいてきfatal
• 致死性ちしせいlethal
• 致死的ちしてきlethal