is a combination of the 副助詞（ふくじょし） (adverbial particle) ばかり, with the conjugated (and negated) form of the 助動詞（じょどうし） (auxiliary verb) だ
. It can be translated as ‘not only (A), (B)’, or ‘not limited to (A), (B).
As ばかり is a 副助詞（ふくじょし）, it may be paired with the 連体形（れんたいけい） (attributive form) of other words.
Not only does he work, but he does house chores too.
Cheap apartments in metropolitan areas aren't only old, but they are usually small and dirty.
This lake is more than just beautiful, there are a lot of alligators, so it is dangerous too.
He won the lottery, and not only did he buy a car, but he also bought a bike and a boat.
Like all other grammar points that negate だ
, several forms may be seen. でなく, でなくて, ではなく, ではなくて
, じゃなく, じゃなくて
. However, it is important to remember that the addition of the は particle will place further emphasis on ない.
is considered to be the more formal version of だけでなく
. This means that だけでなく
will appear far more commonly in everyday speech and writing.
Not only did he not tell his friends, but he didn't even tell his family about moving abroad.
Not only can she play basketball, but I heard that she can swim too.