時間・時点N2
〜次第、〜次第だ、〜次第で（は）
as soon as... / depending on...
Structure
V-ます形（語幹）+ 次第；N + 次第だ／次第で（は）
Explanation
Three uses: ① V-masu + 次第 means "as soon as..., immediately...", with the main clause being the speaker's plan or request; ② N + 次第だ means "depends entirely on..."; ③ N + 次第で(は) means "depending on..., (possibly)...". E.g., 準備ができ次第、出発する; 結果次第では、中止もある.
Examples
資料が集まり次第、すぐにご連絡いたします。
I will contact you as soon as the materials are ready.
成功するかどうかは、努力次第だ。
Whether we succeed depends entirely on our effort.
Note
In sense ① the main clause cannot be in the past tense. With 次第で(は) the main clause often uses speculation (かもしれない, だろう).