Can I say : Invention is something what people invented. Is using what correct? Is there a difference between what and which?
NOT A TEACHER
(1) May I just add a few words to the teacher's excellent answer?
(2) As the teacher told us, we must say:
An invention is something that people have invented.
(a) If you check your books, you will see that the word "that" in your sentence is a
a relative pronoun. The word "relative" means "relate to/ refer to." In other words, the
word "that" relates to the word in front of it: "something." If the word "that" did not
exist, we would have to say something like: "An invention is something. People have invented something." Of course, that is not smooth and not very clear. We are lucky to have relative pronouns.
(i) By the way, sometimes we can delete (erase) a relative pronoun. So this is also
"good" English: An invention is something people have invented.
(3) Let's look at the teacher's second sentence: An invention is what people have
(a) We cannot delete the word "what." English speakers will NOT accept " An invention is people have invented."
(i) "What" is a very interesting word. In your sentence, it actually = two words.
Those two words are "that which."
Therefore, your sentence = An invention is that which people have invented.
I know that it is very difficult to understand all of this. Please post any questions that
you have, and some teachers will give you the answers.
(3) Here are some examples that I have made up. They are not very good, but I think that they will give you the idea:
A car is a vehicle that runs on gas. ("that" = a vehicle. You cannot delete "that".)
A car is a vehicle that many people buy. (You may delete "that.")
Please tell me what you are thinking about. ( = Please tell me that which you are thinking about.)