～わけだ
that’s why / no wonder
～わけだ attaches to the plain form of a clause and draws a logical conclusion from what was just said or noticed. わけ literally means “reason” or “logic”, so the pattern says “the logic works out to X”. In English it's usually translated as “so that's why X”, “no wonder X”, or “that means X”.
1. Drawing a conclusion
Use ～わけだ to restate the natural consequence of facts already on the table, often introduced by つまり (“in other words”).
つまり疲れたわけだ。
“So that's why you're tired.”
- つまり = in other words, in short
- 疲れた（つかれた）= got tired (past form of 疲れる, to get tired)
- わけだ = it follows that, that's why
2. A realization: “no wonder”
When a new fact suddenly explains something puzzling, ～わけだ carries the feeling of “ah, that explains it”.
彼は十年日本に住んでいた。日本語が上手なわけだ。
“He lived in Japan for ten years. No wonder his Japanese is good.”
- 彼（かれ）= he
- は = topic marker
- 十年（じゅうねん）= ten years
- 日本（にほん）= Japan
- に = location marker
- 住んでいた（すんでいた）= was living, lived
- 日本語（にほんご）= Japanese (language)
- が = subject marker
- 上手な（じょうずな）= good at, skilled
- わけだ = no wonder, that explains it
How to form it
Plain form + わけだ (な-adjectives take な before わけ)
- 疲れる（つかれる）= to get tired → 疲れたわけだ（つかれたわけだ）= so that's why (someone) is tired
- 上手だ（じょうずだ）= to be good at → 上手なわけだ（じょうずなわけだ）= no wonder (someone) is good
- 安い（やすい）= cheap → 安いわけだ（やすいわけだ）= no wonder it's cheap
Key idea
～わけだ marks the moment the pieces fit together: given everything just said, X logically follows. If you can paraphrase the sentence with “so that means...” or “no wonder...”, わけだ is the right tool.
Built on the same stem
Updated .