How to say "infection" in Japanese

• 感染かんせんJLPT N1approx.Common
  noun, suru verb, intransitive verbThe general word for infection as the act or state of becoming infected with a disease. Use it when 'infection' means catching an illness or the risk of infection, not the disease itself.
  「トイレの便座べんざからエイズが感染かんせんすることってあるの？」「いいえ、ありません」↗

  "Is it possible to catch AIDS from toilet seats?" "No, it isn't."
• 伝染でんせんJLPT N2approx.Common
  noun, suru verb, intransitive verbCovers infection as contagion — a disease spreading from one person or thing to another. It emphasizes transmission, so it is not the usual word for simply catching or having an infection.
  我々われわれは病気びょうきの伝染でんせんをくいとめなければならない。↗

  We should check the spread of the disease.
• 感染症かんせんしょうCommon
  nounMeans an infectious disease: 'infection' as the illness itself, a disease one is diagnosed with. Choose it when English 'infection' refers to a specific illness or condition rather than the act of becoming infected.
  耳みみの感染症かんせんしょうによくかかります。↗

  I often have ear infections.

Use 感染 for the act or state of becoming infected, 伝染 when the emphasis is on a disease spreading from person to person, and 感染症 when 'infection' means the infectious disease itself.

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

• 感染かんせんinfection
• 伝染でんせんcontagion
• 感染症かんせんしょうinfectious disease
• 化膿かのうsuppuration