We bought a chainsaw which we cut all the wood up withWe cant find the chainsaw that we cut all the wood up with为什么这两个句子一个用that 一个用which

Both "that" and "which" can be used as relative pronouns to refer to a previously mentioned object or idea. However, there is a slight difference in their usage.

"That" is used to introduce a restrictive clause, which means that the information provided by the clause is essential to the meaning of the sentence. In the first sentence, "that" is used to introduce the clause "which we cut all the wood up with," which is essential to understanding what chainsaw was used to cut the wood.

On the other hand, "which" is used to introduce a non-restrictive clause, which means that the information provided by the clause is not essential to the meaning of the sentence. In the second sentence, "which" is used to introduce the clause "we cut all the wood up with," which provides additional information but is not necessary to understand what happened to the chainsaw.

In summary, both "that" and "which" can be used as relative pronouns, but "that" is used for essential information and "which" is used for non-essential information