What Is Their Main Difference?
Parts of Speech
'Where' and 'wherein' function as interrogative adverbs.
'Where' is used to ask about the location of something or someone.
'Wherein' is used to ask 'in what place or respect.'
'Where' is one of the most used words in the English language. 'Wherein,' however, is old-fashioned and informal. 'Wherein' is mostly used in humanitarian articles.
Are They Interchangeable?
'Where' and 'wherein' may be similar in their parts of speech and appearance; however, they cannot be used interchangeably as they express different meanings.