Nonrestrictive vs restrictive

Question

Hi, could you help me?"This car which runs on liquid hydrogen attains a top speed of 90 mph.""This car, which runs on liquid hydrogen, attains a top speed of 90 mph."Which is correct? If both are OK, are there any differences between them?If I replace "this" with "that" in the sentences above, which is correct?"That car which runs on liquid hydrogen attains a top speed of 90 mph.""That car, which runs on liquid hydrogen, attains a top speed of 90 mph."Are there any differences?

Vsuresh · Accepted Answer

The second one is correct.

The car which runs on liquid hydrogen attains a top speed of 90 mph. (Restrictive; no comma)

Changing this to that or vice versa does not affect the use of comma.

This/That car, which runs on liquid hydrogen, attains a top speed of 90 mph.(Non restrictive; comma is essential)

Tashiro · Answer

Thank you.

Mister Micawber · Answer

There seems to be some confusion.

This car, which runs on liquid hydrogen, attains a top speed of 90 mph.

That car, which runs on liquid hydrogen, attains a top speed of 90 mph.

'This' and 'that' both identify the car (in context, of course), so both non-restrictive clauses require commas. A sentence containing a restrictive clause in such a context would read something like this:

A car which runs on liquid hydrogen can attain a top speed of 90 kmph.

Vsuresh · Answer

Thank you, Mister Micawber.

Tashiro · Answer

Thank you.

Miriam · Answer

Depending on ther context, you can very well say:

"That car which/that runs on liquid hydrogen (as opposed to some other car) attains a top speed of 90 mph." (As opposed to some other car of similar characteristics but which cannot reach such speed.)

The above sentence is correct. In it, not only the speed is "new" information, but also the fact that the car runs on liquid hydrogen. In that case, you don't use commas (the relative clause is restrictive) because the information is necessary to understand the rest of the sentence for some reason, such as the èrson you're talking to not knowing what the car uses for fuel.

You use the commas (a non-restrictive relative clause) when the information between the commas is not necessary for understanding the sentence or the listener already knows it.

You can use "the", "that" or "these" in the main clause. It all depends on the context/situation.

By the same token, you can also use a non-restrictive relative clause (one set off from the rest of the sentence by commas), depending on the context. While it would be nonsense to say "A car which is a type of vehicle runs fast" when all the people involved in the conversation know what you are talking about, there is nothing wrong with saying, for example, the following: "A car, which is an effective means of transport, can attain a top speed of 90 mph if it runs on liquid hydrogen."

Again, it always depends on the situation and on what you wish to say. This said, there are certain rules thatmuct be respected. For example, you cannot start a non-restrictive relative clause with the relative pronoun "that". It is correct only in restrictive relative clauses

Don't confuse "that car is fast," in which "that" is a demonstrative adjective, with "the car that is parked nearby is not mine," in which "that" is a relative pronoun introducing a restrictive relative clause.

Hope this is not confusing.

Cheers!

Miriam

Nonrestrictive vs restrictive

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