What as “the thing that”: a nominal relative clause
In the English sentence “I bought what they recommended,” what, together with everything that follows it, forms one noun phrase. English needs only one word, what, for this purpose: it refers to a thing and at the same time serves as the subject or object within its own clause.
This construction is called a nominal relative clause. A simple test is to replace what with the thing(s) that. If the sentence keeps the same meaning, it is this construction, not a question.
what + (subject) + verb ≈ the thing(s) that + …
- subject / S —
- The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
- verb / V —
- A word for an action or state, such as work or be. The pattern determines its form.
My neighbour never returns what he borrows.
My neighbour never returns the thing(s) that he borrows.
What he borrows = the things that he borrows; what is the object of borrows.
We sold what we didn't need.
We sold the thing that we did not need.
The clause what we didn't need became the object of sold and names the item that was sold.
What role does the clause play in the sentence?
A noun phrase can appear in different places in a sentence, and a what-clause is no exception. It can be the subject at the beginning, the object after a verb, the object after a preposition, or a complement after be.
A preposition before the entire what-clause belongs to the outer construction: proud of what her students have built. If the preposition is connected to a verb inside the clause, it often appears at the end: what they talked about. These are two different positions, and they can coexist.
What the architect proposed was too expensive.
The thing that the architect proposed was too expensive.
The clause is the subject; the main verb was comes immediately after it.
The pilot checked what the instruments showed.
The pilot checked the thing that the instruments showed.
The clause is the object of checked.
She is proud of what her students have built.
She is proud of the thing that her students have built.
The clause comes after the preposition of and is governed by it.
That is what the label says.
That is the thing that the label says.
After be, the clause names what the subject is.
What stands inside the clause: what versus that
What does more than join a clause: it identifies an element inside it, such as the thing someone wants or the thing that caused an event. That in a content clause does not replace such an element: He said that he wanted a break.
A useful question is: does what refer to an object, an action, or the meaning “the thing that”? In he wanted what, it is the object of wanting. Do not rely only on whether the remainder is grammatical without what: some verbs allow an omitted object. Check the meaning of the whole construction.
The engineers replaced what caused the leak.
The engineers replaced the thing that caused the leak.
What is the subject of caused: without it, the clause has no subject.
He said what he wanted.
He said the thing that he wanted.
Wanted has an object expressed by what.
He said that he wanted a break.
He said that he wanted a break.
The clause after that is complete: the object a break is already present, so that is needed to connect the clauses.
Direct word order and agreement
Inside a what-clause, there is no question inversion: what you want, not what do you want. This does not rule out the auxiliary do for negation or emphasis: what you don’t want, what you do want. If what is the subject, do not add a separate subject: what caused the leak.
A what-clause used as the subject often takes a singular verb: What the visitors liked was the garden. The plural noun visitors inside the clause does not determine this agreement. However, with be and a plural complement, are/were is possible: What we need are two chairs. This is a standard option, not merely a conversational deviation.
Do not use a comma between the subject clause and the predicate.
Nobody checked what the courier delivered.
Nobody checked the thing that the courier delivered.
The clause has direct word order and the ordinary form delivered, without did.
What the visitors liked was the garden.
The thing that the visitors liked was the garden.
The subject is the entire clause, so the verb is singular, although visitors is plural.
What or that, which, everything that
Use what when there is no noun phrase before the clause. If there is a noun phrase, the introducer is that or which, or often nothing: the thing that you promised, everything that she said, the only book you borrowed. “Everything what” and “the thing what” are typical mistakes.
Which after a comma comments on the entire preceding situation and does not introduce a noun phrase: He apologised, which pleased everyone. What does not have this role. Forms ending in -ever (whatever, whoever) have a different meaning, “anything that” or “anyone who,” and are not covered in this lesson.
Everything that the guide mentioned was on the exam.
Everything that the guide mentioned was on the exam.
Because everything comes before the clause, the introducer is that, not what.
The only thing that matters is honesty.
The only thing that matters is honesty.
After the only thing, that is needed: what would be unnecessary.
She waved, which pleased the children.
She waved, which pleased the children.
Which comments on the entire preceding action and does not function as a noun phrase.
Do not confuse it with a question or an emphatic cleft
The same word what can also ask a question. In “She asked what time the museum opens,” the clause is an indirect question about the time, and the thing that is not appropriate here. The substitution test helps distinguish them: whatever can be replaced by the thing(s) that is a what-clause meaning “the thing that.”
A subject clause with be can also highlight an important element of the sentence (this is how an emphatic what-cleft works; it is covered in a separate rule). Here we are treating the clause as an ordinary noun phrase and are not teaching how to highlight a sentence element with it.
I wonder what the guard is looking at.
I wonder what the guard is looking at.
This is an indirect question: replacing it with the thing that is impossible.
I can point out what the guard is looking at.
I can point out what the guard is looking at.
Here the clause names an object, so replacing it with the thing that preserves the meaning.
How to use it in your own speech
What-clauses make speech more concise: instead of “the things that…,” you name the thing with one word. They sound natural in expressions of gratitude, evaluation, requests, reports, and instructions.
A useful habit is this: before writing, mentally name the clause as a noun phrase (“the thing that he proposed”) and ask what role it plays in the sentence. The preposition will then fall into place naturally.
I believe in what we are building here.
I believe in the thing that we are building here.
The clause after the preposition in names the object of belief.
Please keep what you have written so far.
Please keep the thing that you have written so far.
A request with an object clause; the word order is direct.
What you promise in the first meeting matters later.
The thing that you promise at the first meeting matters later.
A subject clause; the verb matters is singular, with no comma before it.
Common mistakes
Incorrect:What the team needed were a better plan.
Correct:What the team needed was a better plan.
The subject is the entire clause, so the verb is singular; the complement a better plan is singular as well.
Incorrect:I'm looking for the thing what you promised.
Correct:I'm looking for the thing that you promised.
The noun phrase the thing already appears before the clause, so the introducer must be that or which; what is used without such a noun.
Incorrect:Tell me what do you want.
Correct:Tell me what you want.
There is no question inversion in the subordinate clause: you comes before want. The emphatic version what you do want is also possible, but it has different emphasis.
Incorrect:Which she suggested was sensible.
Correct:What she suggested was sensible.
A subject clause without a noun before it is introduced by what; which needs an antecedent or comments on the preceding situation.
Incorrect:You should avoid what they warned you about it.
Correct:You should avoid what they warned you about.
What is already the object of about, so the pronoun it at the end is unnecessary.
Incorrect:What he said, was true.
Correct:What he said was true.
Do not use a comma between the subject clause and the predicate.