day by day

他一天天变得更强壮。

___Day ___by ___day he grew stronger.

天气一天天变得越来越暖和，没有人想念冬天的雨和严寒。

The weather gets warmer and warmer ___day ___by ___day, and no one misses the rain and severe cold of winter.

我交到了朋友，在学习上也一天比一天更自信。

I made friends and became more confident in my studies ___day ___by ___day.