温故知新的英文：
[Literal Meaning]
review/old/know/new
to gain new insights through reviewing old material

[解释]
温：温习；故：旧的。温习旧的知识，得到新的理解和体会。

[Explanation]
to review what have been learned and learn something new

[例子]
温故知新，同学们在寒假里一定要把这学期学过的知识再复习一下。

[Example]
To review what have been learned you can learn something new. You must review what we have learned in this semester in the winter vacation.

[英文等价词]
gain new insights through reviewing old material