Understanding when to use good at and good in is key to mastering English. Use good at before a verb to talk about skills. For example, “She is good at painting.” This means she has talent …
be good at和be good in的区别是：be good in是表现良好，有效果，但be good in 极少作固定短语，后接名词。 擅长于某事，at后接名词或动名词，即动词加ing。 Alex is very good at languages。
Generally, someone is good at doing something. On the other hand, someone is [simply] good in something. However, depending on which dialect you are speaking in, it depends. For instance, …
There's only one major case that leaps to mind where "good in" is idiomatically correct: He is good in bed. This can be generalized somewhat to "he is good in (location where certain …
There are some idiomatic expressions where “good in” is appropriate, but these are rather rare. The most common one is “to be good in bed”:
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