再発（さいはつ、saihatsu）
- recurrence

The Japanese word 再発 （さいはつ） means "recurrence," "relapse," or "reappearance." It is most commonly used in medical contexts to describe the return of a disease or condition after a period of remission or improvement. However, it can also be used in other contexts to refer to the повторение of an event or problem. The core idea is something that happened previously happening again. This often implies a negative or unwanted situation.

⚫︎病気が再発した。 Translation: The illness relapsed. ⚫︎あの問題がまた再発した。 Translation: That problem reappeared again. ⚫︎再発防止のために、対策を立てましょう。 Translation: Let's create measures to prevent recurrence.

⚫︎再発 is a formal word. ⚫︎It is often used in medical, legal, and business contexts. ⚫︎Use it when discussing the return of a disease, a problem, or an unwanted event. ⚫︎It is suitable for both written and spoken Japanese in formal settings. ⚫︎Can be used in a conversation to express concerns or to describe the continuation of a negative situation.

⚫︎The word is written with the kanji 再（さい - meaning "again," "re-") and 発（はつ - meaning "to start," "to develop," "to emit"). ⚫︎The reading is さいはつ. ⚫︎It is always written in kanji. ⚫︎There are no variations in okurigana for this word.

⚫︎再燃（さいねん - relapse, renewed outbreak): This is used in a medical context, particularly for the return of inflammation or other conditions. ⚫︎繰り返す（くりかえす - to repeat): This is a more general term for repeating something. ⚫︎復活（ふっかつ - revival, resurrection): This can be used if something is coming back after stopping.

⚫︎寛解（かんかい - remission): This is the opposite in a medical context, meaning the temporary or permanent cessation of a disease. ⚫︎治癒（ちゆ - cure): This implies complete recovery and no possibility of recurrence. ⚫︎改善（かいぜん - improvement): This is a general term describing a positive change.

癌が手術後、一年経って再発しました。 ・Translation: The cancer relapsed a year after the surgery. ・Explanation: This sentence describes the recurrence of cancer after a period of remission, highlighting the use of 再発 in a medical context.

この問題の再発を防ぐためには、根本的な解決策が必要です。 ・Translation: To prevent the recurrence of this problem, a fundamental solution is needed. ・Explanation: This sentence illustrates the use of 再発 in a broader context, discussing strategies to prevent the repetition of a problem.

The word 再発 is formed from two kanji. 再 means "again" or "re-," and 発 means "to start," "to develop," or "to emit." Together, they combine to mean "to occur again" or "to relapse." The etymology reflects the core meaning of the word: something that had happened before is happening again.