phrase B2 every day, or more and more as each day passes: 每天，天天;日益，越来越 Day by day he became weaker.他的身体日渐虚弱。 These birds are disappearing day by day as their habitat shrinks. His anger grew day by day. The demand for this product is increasing day by day. The situation is grave and worsening day by day. Day by day, his hopes grew stronger. See also
day
day by day | American Dictionary
day by day
idiom gradually over many days: Day by day my father grew stronger.