Coconut oil produces a soap "which/that" will lather in saltwater as well as fresh.

The teacher said "that" though I thought "which".

Can someone please elaborately explain where we use "which" & "that". I'm having lots of problems to correctly use it? Please explain in details.


2 Answers 2


Generally, "which" and "that" are interchangeable in integrated (defining) relatives, but supplementary (non-defining) that relatives are virtually always inadmissible.

There are a few places where a non-wh relative is preferred. For example after "all" and the compound determinatives "anything", "everything" etc.:

All [(that) I want] is a little peace and quiet.

Anything [(that) you say] may be used in evidence.

And in the case of nominals with superlative modifiers, again the non-wh is preferred:

She gave me the best meal [(that) I'd had in a long time].

That fish is the biggest [(that) I've ever seen].


"Which" and "that" are used only in identifying (defining/restrictive) clauses. Ex: Where is the girl who/that sells the ticket? We can use both of them because the relative clause mentioned in here is an essential part of the sentence. If we remove that, the meaning of the sentence will be incomplete.

On the other hand, just "Which, where, what, etc." is used in non-identifying (non-defining/non-restrictive) clauses. Ex: This is Julia, who sells the ticket. Normally, we use this type of relative clause between commas. And as it's clear, you can remove that sentence and the meaning of the sentence will be complete.

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