when to use relative pronouns 'that' &'when' in a statement?
Time..........(that / which / when) is lost is never found again.
explain with reason.
We use “that” as a relative pronoun with restrictive clauses. Restrictive clauses limits the subject or makes the subject more specific. We do not use a comma before “that”.
We use “when” as a relative pronoun when we mean to say “since what time?” For example: “My mother fears water, since when my grandfather drowned in the river in front of her and she could not help him.”
“Which” is used as a relative pronoun with non-restrictive clauses. A non-restrictive clauses talks about the subject generally and not specifically. We use a comma before "which".
If we take the sentence provided by you as an example, here “that” would be the most appropriate answer. Here “Time has been specified as something that is lost”. "Which" is inappropriate because there is no comma in the sentence. “When” is totally incorrect as it makes no sense.