防微杜渐 – fang2wei1du4jian4
Literal meaning of each character :
guard/prepare against/prevent – minute/tiny/slight – stop/prevent/eradicate – gradual
Luckily in English we have an equivalent idiom with a similar meaning “Nip evil in the bud”.
When analyzing the 4 characters above used in this idiom you can see the meaning easily. You are guarding against small or minute things, stopping them from gradually becoming anything else.
This idiom can be used in any situation where you would use the English idiom “Nip evil in the bud” and therefore I don’t think it’s necessary to go into too much detail with examples of how and when to use it.
There are quite a few Chinese idioms that have equivalent Chinese meanings. This is great for explaining how and when to use these common sayings. However, there are also many that have absolutely no equivalent in English and therefore require extensive explanation and examples so as to understand fully the meaning and in what situations one can properly use it.