day by day; every day; with each passing day
Formal or literary adverb emphasizing a gradual daily progression. Often used in written or official contexts.
The situation is changing day by day.
Please submit a daily work report.
Compound of 逐 (pursue, follow in order) and 日 (day), literally 'following the days'. The reading ちくじつ is the on'yomi of both characters.