grammar - that vs which vs what

Temporary reopen note:

Pleas note that this other question here does not address what or compare it to which or that:

---

Original Question

• Which sentence would you use more, which is just simple wrong and why?

This is the speech, that my father wrote.
This is the speech, which my father wrote.
This is the speech, what my father wrote.

This is the speech, that my father wrote down.
This is the speech, which my father wrote down.
This is the speech, what my father wrote down.

Answer

1. This is the speech, that my father wrote (down).


2. This is the speech, which my father wrote (down).


3. This is the speech, what my father wrote (down).

The vocabulary

The difference between write and write down is quite subtle. Write down implies that whatever was written existed in some other form before it was written down. So it might have been a fully formed idea, or someone may have read it out. Write on its own just means write. If we just use wrote, it gives the impression that it was actually the father's speech. However, if we use wrote down it might be someone else's speech that was written down. For example, a speech from the television.

The grammar

There are some problems with all of the sentences as they stand. These sentences almost definitely contain so-called defining relative clauses, and so don't need a comma.

In defining relative clauses like this we can use either which or that as a relative word:

• This is the speech that my father wrote.


• This is the speech which my father wrote.

Here the word speech is the antecedent for the relative clause. There is a gap in the relative clause after the verb wrote where we would expect an object. We understand that gap as having the same identity as the speech:

• This is the speech_(i) that my father wrote ____ _(i).



• This is the speech_(i) which my father wrote ____ _(i).

Notice that the relative clauses here are modifying the word speech. They are turning it into one big noun phrase. "This is the speech" Which speech? "The [speech that my father wrote]".

However, we cannot use a relative clause with what to modify a noun in this way. We only use the relative word what when there is no antecedent for a relative clause:

• *This is the speech what my father wrote. (Ungrammatical - what with antecedent)


• This is what my father wrote. (Grammatical - no antecedent)

In the second sentence above, what does not have an antecedent. The relative does not have an antecedent. Instead the whole clause is the complement of the verb BE. The first example is ungrammatical because it uses what with an antecedent.

The Original Poster's Question:

The following sentence is incorrect in standard English because it uses an antecedent for the relative word what:

• This is the speech what my father wrote.

The following, however, are both fine:

• This is the speech that my father wrote.


• This is the speech which my father wrote.

In this case because there is a subject after the relative word (that or which), we can leave out the relative word:

• This is the speech my father wrote.

Hope this is helpful!

[Note: Some bogus usage guides say that which should not be used for defining relative clauses. This is rubbish. It is harmful to the study of Englsih grammar, and it has never been true. All the best writers have used both which and that for defining relative clauses.]