English translation:
not only but also
let alone
not to mention
Structure:
Noun + はもちろん + Noun(も/さえ)
Explanation:
[AはもちろんBも - A is natural/obvious, and by the same logic, B is also true・more formal “not only, but also” pattern than だけでなく]
If anyone is looking for a more in-depth structure on how to use this not just with nouns, but with verbs and adjectives check out Yuka Sensei’s lesson on this 
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I’m having trouble distinguishing between はもちろん and ばかりでなく. Are the interchangeable?
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@ljoekelsoey
Hey 
Those expressions are mostly interchangeable. Notice the differences in conjugation though!
はもちろん can only follow nouns (of course it can also follow verbs/adjectives nominalized with こと、but not directly).
ばかりでなく can follow nouns, verbs, adjectives directly, without nominalizers. (remember to add な if it follows なadjective though)
Another thing is that はもちろん is more indirect. That is, “not only, but also” is implied. ばかりでなく on the other hand simply means “not only but also”.
I hope it helps,
Cheers!
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