Describes doing or processing things sequentially, emphasizing a steady, step-by-step progression. Often used with verbs like 片付ける, 消える, 増える, etc.
He solved the problems one by one.
星が一つまた一つと消えていった。
The stars disappeared one after another.
Standard kanji-kana mixed spelling.
Variant using the kanji 又 for また; less common but still seen.
A fixed expression composed of 一つ (one) + また (again) + 一つ (one), literally 'one, and again one'. The repetition emphasizes sequential occurrence.