on Writing Forward:
There’s a lot of confusion about that and which. These two words are often used interchangeably, even though they’re not necessarily interchangeable.
Historically, that and which may have carried the same meaning, and some English dialects may allow for that and which to be swapped without affecting the meaning of a sentence.
However, in American English, the grammar rules offer a distinct difference between the two words. By the time you’re done reading this post, you’ll fully understand the difference between that and which, and you’ll be able to use both words correctly.