In Which vs Wherein?

The grammatically correct substitution for wherein is "in which". Replacing wherein with where is one of those cases that is probably incorrect in a technical sense, but it's used enough that people will understand you and it won't sound unnatural.

How do you use wherein in a sentence?

Examples of wherein in a Sentence

Conjunction the city wherein he lives There was a period in her life wherein she took no active part in politics. He showed me wherein I was wrong.

Do I use where or in which?

'Where' must relate to a place

So it's up to you to decide whether to use “which” or “where” in your particular sentence. If your audience expects formal grammar, consider using a “which” construction. If your audience is more relaxed, you can use “where.”