のみならずNot only...but, Not just...but, What is more

のみならず and だけでなく are essentially synonymous in that they both express non-exclusivity (i.e. 'not only'), but differ in formality. While だけでなく is common in both everyday speech (often appearing as だけじゃなくて) and writing, のみならず is a highly formal expression used primarily in writing and academic contexts. Both phrases are often followed by a noun + も to convey 'not only (A), but also (B)'.

ばかりでなく and のみならず are both expressions used to convey the meaning of 'Not only (A)'. While both are formal, のみならず is even more literary. Both patterns can also be followed by noun + も to express 'But also (B)'. For example, 日本語のみならず、韓国語も話せる 'He can speak not only Japanese, but also Korean.' vs. 日本語ばかりでなく、韓国語も話せる (Same meaning, but slightly less literary in tone).

のみならず and だけでなく(て)～も are nearly identical in meaning, both meaning 'Not only (A), but also (B)'. のみならず is by far the more formal expression, while だけでなく (especially in the alternate form だけじゃなくて) is more common in everyday speech. For example, 日本語のみならず、韓国語も話せる 'He can speak not only Japanese, but also Korean.' vs. 日本語だけじゃなくて、韓国語も話せる (Same meaning, but far more casual).

だけ conveys 'only' or 'just.' In contrast, のみならず is a formal expression similar to だけじゃなく, meaning 'not only A, but also B.' While だけ expresses limitation, のみならず emphasizes a lack of restriction. Note that while だけ is commonly used in both everyday speech and writing, のみならず is more formal and typically limited to written language or formal speech.