connective N3 common casualpolitewritten

せい — the fault / cause of (something bad)

せい

Meaning

the fault of ~ / because of ~ (something bad) — a noun blaming an undesirable result on a cause

せい is a noun meaning 'the cause to blame'. As 〜のせいだ it pins a bad outcome on someone or something (君きみのせいだ, 'it's your fault'); 〜のせいか hedges it ('maybe because of ~'). The defining feature is *negative valence* — せい assigns blame, the exact opposite of おかげ ('thanks to'). The connective form is せいで.

Key sentence

負まけたのは私わたしのせいだ。

We lost, and it's my fault.

Formation

Attaches to	Form	Example
Noun + の / plain clause / na-adj な / i-adj + せい	Nの / 〜 plain + せい(だ/か)	天気てんきのせい / 年としのせいか

Examples

失敗しっぱいを人ひとのせいにするな。

Don't blame your failures on others.

気きのせいかもしれない。

It might just be my imagination.

寝不足ねぶそくのせいか、頭あたまが痛いたい。

Maybe because I'm short on sleep, my head hurts.

Easily confused with

おかげ Polar opposites in valence: せい blames a *bad* result on a cause ('your fault'); おかげ credits a *good* one ('thanks to you'). 〜せいでせい is the noun ('the fault'); せいで is its connective form linking the cause to the bad result that follows ('because of ~, [bad thing happened]').

Notes

〜せいにする = 'blame on ~' (人ひとのせいにする). 〜せいか softens to 'perhaps because' when you're unsure of the cause.

See せい in real sentences

Jengo shows せい the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.

Study it in Jengo

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