to be attached; to be connected with; to remain imprinted; to scar; to bear (fruit, interest, etc.); to be acquired (of a habit, ability, etc.); to increase (of strength, etc.)
Examples (4 in total)
その時は、まだねついてなかったよ。
I wasn't yet asleep at that time.
興奮していたので、私はねつかれなかった。
I was so excited that I couldn't fall asleep.
眠いけど、まだねつけない。
I'm tired, but I still can't fall asleep.
最近気がかりなことがたくさんあって、夜ねつくのに苦労している。
I've had a lot on my mind recently and have had trouble falling asleep at night.