How to tell them apart
Both point to a cause for a bad outcome, but ばかりに stresses that one single, often minor or unfair factor is the whole reason things went wrong, carrying a sense of "if only that hadn't happened." せいで simply blames a cause for an undesirable result and is commonly used to pin fault on someone or something, as in 誰のせいでもない. Swapping them feels off because ばかりに sounds too dramatic for a neutral blame statement, while せいで lacks the "just because of that one thing" nuance.
- ばかりに Use ばかりに when one small or specific factor alone triggers an unfortunate result.
- せい Use せいで when you want to blame a cause or someone's fault for a bad outcome.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| ばかりに bakarini | merely for the reason that | N2 |
| せい sei | owing to, for the fault of (unfavorable cause) | N3 |
ばかりに bakarini
merely for the reason that
ばかりに marks a single cause that led to a bad or regretted result, with the sense of only because of that action. It follows the past tense plain form of a verb, as in 急いだばかりに or 油断したばかりに. The following clause must express an unfortunate outcome, so it cannot be used for neutral explanations or positive results.
-
急いだばかりに、財布を忘れてしまった。
Just because I was in a hurry, I ended up forgetting my wallet.
-
安いものを選んだばかりに、すぐ壊れた。
Just because I chose the cheap one, it broke right away.
せい sei
owing to, for the fault of (unfavorable cause)
せい expresses that something is the unfavorable cause of a bad result, often with a nuance of blame or complaint. It follows nouns with の, as in 雨のせいだ, plain verbs and i-adjectives directly, and na-adjectives with な. Common patterns include のせいだ to identify the cause, のせいで to connect it to a result, and のせいにする to blame someone for a mistake. It is not used for positive outcomes.
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彼らの到着が遅れたのは雨のせいだ。
Their late arrival was owing to the rain.
-
自分の誤りを人のせいにしてはいけない。
Don't blame others for your own fault.
ばかりに and せい are JLPT N3–N2 grammar points that Japanese learners often mix up. This page compares them side by side on meanings, usage and example sentences, so you can tell them apart.