「〜のは〜せいだ」- The reason... is because...

Explanation

「〜のは〜せいだ」 is a Japanese grammatical structure used to express the cause or responsibility behind a certain outcome, meaning "The reason... is because...". It is often used to explain the cause of a result, typically with a negative or blaming tone.

Grammar Pattern

Grammar Point	Connection	Explanation
〜のは〜せいだ	Verb/Adjective/Noun + のは + Verb/Adjective/Noun + せいだ	Indicates the cause of a certain result, often with a negative or blaming tone.

Basic Usage

Connection

• Verb plain form + のは + Verb/Adjective/Noun + せいだ
• Adjective plain form + のは + Verb/Adjective/Noun + せいだ
• Noun + な + のは + Verb/Adjective/Noun + せいだ

Meaning

• Indicates the cause of a certain result, often with a negative or blaming tone.

Examples

• 寝坊ねぼうしたのは昨日きのう遅おそくまで起おきていたせいだ。
• Nebou shita no wa kinou osoku made okiteita sei da.
• The reason I overslept is because I stayed up late last night.
  

• 試験しけんに落おちたのは勉強べんきょうしなかったせいだ。
• Shiken ni ochita no wa benkyou shinakatta sei da.
• The reason I failed the exam is because I didn't study.
  

• 頭あたまが痛いたいのは風邪かぜを引ひいたせいだ。
• Atama ga itai no wa kaze o hiita sei da.
• The reason my head hurts is because I caught a cold.
  

• 彼かれが怒おこっているのは私わたしの言葉ことばのせいだ。
• Kare ga okotteiru no wa watashi no kotoba no sei da.
• The reason he is angry is because of what I said.
  

Comparison and Differences

Although both 「〜のは〜せいだ」 and 「〜のは〜からだ」 are used to explain reasons, they differ in tone and usage.

Grammar Point	Tone	Usage
〜のは〜せいだ	Negative or blaming	Often used to express bad outcomes or blame someone
〜のは〜からだ	Neutral	Used for general explanations of reasons

Example:

• 遅刻ちこくしたのは電車でんしゃが遅おくれたからだ。
• Chikoku shita no wa densha ga okureta kara da.
• The reason I was late is because the train was delayed.
  

Deep Dive

「〜のは〜せいだ」 is primarily used to express the cause of a certain result, often with a negative or blaming tone. It emphasizes the causal relationship between the result and the cause, and is commonly used in everyday conversations.

Summary

「〜のは〜せいだ」 is a Japanese grammatical structure used to express the cause or responsibility behind a certain outcome, meaning "The reason... is because...". Mastering this structure will help you better explain reasons and express blame or dissatisfaction in daily conversations.