Confused about when to use that or which? You’re not alone — this is one of the trickiest grammar points, even for native speakers!
That is used to give essential information — information that is necessary to understand the sentence. There are no commas around it.
Use that when the information tells you *which one* or *which kind* specifically.
Which is used to add extra (non-essential) information. The sentence would still make sense without it. It's usually set off by commas.
Use which when the detail is interesting but not necessary to identify the thing you’re talking about.
If the information is essential → use that (no commas).
If it’s just extra info → use which (with commas).
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