by the day
• gradually and steadily.
• "the campaign is growing by the day"
day by day
• on each successive day; gradually and steadily.
• "day by day I grew worse"
Similar:
gradually,
bit by bit,
by degrees,
by stages,
inchmeal,
inch by inch,
little by little,
step by step,
slowly,
slowly but surely,
steadily,
progressively,
daily,
every day,
day after day,
a day at a time,
diurnally,
Opposite:
all at once,
