〜ばかりか／ばかりでなく
Not only… but alsomachine translation
FormationNoun / verb or adjective in plain form + ばかりか／ばかりでなく、… + も／まで
A ばかりか B: "not only A but also B" — B is something weightier and more surprising than A: 彼は英語ばかりか、中国語も話せる (he can speak not only English but even Chinese). Clause B usually takes も or まで to push the degree up.
ばかりでなく means the same but is softer and more widely used, comfortable in both speech and writing: 自分の仕事ばかりでなく、私の仕事も手伝ってくれた. You already know だけでなく — ばかりでなく is one step more formal, while ばかりか is the most literary of the group and CANNOT be used when the following clause is a command, invitation, or expression of intent.
The pattern works just as well in the negative direction: この薬は効かないばかりか、体に悪い (this medicine not only doesn't work but is bad for you). A close relative: はもちろん — but はもちろん treats A as something obvious that everyone knows, while ばかりか simply stacks B on top of A.
Examples
彼は英語ばかりか、中国語も話せます。
He can speak not only English but also Chinese.
この薬は効かないばかりか、体に悪いそうです。
I hear this medicine not only doesn't work but is actually bad for your body.
彼女は自分の仕事ばかりでなく、私の仕事も手伝ってくれました。
She not only did her own work but also helped with mine.