なく

Inflection Ending (used in writing and formal speech only) (Intermediate ㊥ 211)

a continuative form of ない used in written Japanese (to indicate a reason/cause for what follows if ない is attached to Adjective (い/な) and contrast if it is attached to a Noun+Copula).

Equivalent: Not ~ and; not ~ but

日本語の期末試験はあまり難しくなく、ほっとした。
The Japanese final examination was not very hard, and I felt relieved.
私の研究対象は現代史ではなく、古代史だ。
My research area is not modern history, but ancient history.
今年の冬はあまり寒くなく、オーバーも二、三度しか着なかった。
It wasn't very cold this winter and we wore our overcoats only two or three times.
昨日見た映画は実に面白くなく、途中で寝てしまった。
The movie I saw yesterday was so boring that I went to sleep during it.
私には日本語を聞くのが容易ではなく、大分苦労した。
To listen to Japanese was not easy, and I had quite a difficult time.
彼女と別れた時はそれほど悲しくなく、自分でも驚いた。
I was surprised that I did not feel so sad when I parted with her.
私には日本語を教えてくれたのは日本人ではなく、アメリカ人だった。
The person who taught me Japanese was not a Japanese but an American.
僕が好きなのは日本料理ではなくタイ料理だ。
What I like is not Japanese cuisine, but Thai cuisine.

Formation

(i) Adjective い stemくなく
大きくなくSomething/someone is not big and ~
(ii) {Adjective な stem/Noun}ではなく
静かではなくSomething/someone is not quiet and ~
先生ではなくSomeone is not a teacher but ~

Notes