Step by step; gradually and steadily, one step at a time. Used as an adverb for progressing in stages (work, recovery, learning, etc.).
大きな目標も一歩ずつ進めば達成できる。
Even large goals can be achieved if you move forward one step at a time.
手術後は回復が一歩ずつ進んでいると聞いた。
I heard that the recovery after the surgery is progressing step by step.
プロジェクトは一歩ずつ着実に進行している。
The project is progressing steadily, one step at a time.