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This question already has an answer here:

What did you say?
What you said.

How did you and mum guess I wanted Agnes?
how you and Mum guessed I wanted Agnes

What is the meaning of above two sentences?
When should I use "did + present tense" and the past tense of a verb?

marked as duplicate by ColleenV Oct 6 '17 at 14:24

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • is it correct to say- "did you WANTED that to be done?" – user5349 Mar 27 '14 at 11:54
  • @shreya - No, it's "Did you want that to be done?" Feel free to ask one of your own questions for more information. – J.R. Mar 27 '14 at 12:14
4

"Did" is often used in English in questions to turn a statement into a question.

People who are learning English are often tempted to turn a statement into a question by simply adding an interrogative word like "how" or "why" to it.

Statement: You gave him the box.

Attempt at question - WRONG: Why you gave him the box?

To make a proper question, you must change the verb from past tense to "did" plus present.

Question - RIGHT: Why did you give him the box?

I can't give you a good reason why you need to do this. It's just how it's done in English.

Perhaps I should clarify that that's not the only way to phrase a question.

If the action is in the future, we are already using a helping verb like "will". In this case we move the word "will" to precede the subject, but otherwise keep the same verbs.

Statement: You will give him the box.

Question: When will you give him the box?

Likewise if the original statement is in the present continuous, like "are giving".

Statement: You are giving him the box.

Question: Why are you giving him the box?

If the statement is in the present tense, we add the word "do".

Statement: You think the box is full.

Question: Why do you think the box is full?

8

Part 1

In English, the basic sentence structure of a declarative statement is "subject aux verb object". Aux stands for an auxiliary verb which may be missing.

For instance, "You have read the book". The subject is "you", the auxiliary verb is "have", the verb is "read".

When questions are formed, a transformation called "subject-aux inversion" takes place, and so we have "aux subject verb object?" "Have you read the book?"

Some sentences do not have an aux. For instance:

"You ate breakfast".

In this situation, we can pretend there is an empty/null auxiliary:

"You {0} ate breakfast"

When the question is formed, subject-aux inversion takes place with the empty aux, and we obtain

"{0} you ate breakfast?"

It's an observed fact of English that we cannot have this null auxiliary at the start of a sentence. A process takes place called "do affixing" whereby the empty auxiliary is replaced by the helping word "do". This word doesn't add any meaning; it serves a grammatical role. And when we replace {0} with do, we get:

"Do you ate breakfast?"

Oops, this is still not quite right. One more rule takes place. Whenever we have an auxiliary present with a verb, the verb never takes the past tense. The verb can be a past participle, like "been" in "have been", or just a plain form like "be" in "should be". A form like "have was" is not grammatical because there is an auxiliary verb, and the main verb has past tense. The past tense, if any, has to be on the auxiliary verb, like in "had been": "had" is past tense, "been" is a past participle.

Similarly when the word "do" is the auxiliary, it has to take the past tense. "Do ate" is not grammatical. The past tense has to be transferred from "ate" to "do" to form "did eat". And that gives us the grammatically correct question:

"Did you eat breakfast?"

So that is how you can understand why the "did" is there. It's an auxiliary which is inserted to replace a null auxiliary once subject-aux inversion takes place (do affixing), and at the same time "steals" the past tense from the main verb, because auxiliaries have to carry the tense when they are present!


Part 2

So let us now look at "what did you say" versus "what you said".

Firstly, what you said is a "wh-clause". The prototypical sentence for a wh-clause is still "subject aux verb object" type syntax, such as:

you said what

In English, in a wh-clause, the wh-word (who, what, when, ...) undergoes a transformation: it moves to the front of the sentence:

what you said

"What you said" is not a question. It is a clause which refers to something, functioning as a noun. In other words, a nominal clause.

In this case, it refers to something which was said by "you". For example: "I did not hear what you said. Can you repeat it?" Which means, "I did not hear the words you spoke. Can you repeat those words?" The clause "what you said" has the same meaning as "the words you spoke"; it functions much like a noun.

"What did you say?", on the other hand, is a question and not a nominal clause. It is formed like this: start with the prototypical sentence (subject verb object):

you said what

Then subject-aux inversion, with do-affixing takes place, to form a prototypical question:

did you say what

Lastly, the wh-word must move to the front of the sentence:

What did you say?

(Note, however, that "You said what?" is a possible question and is grammatical, yet there is no movement of the wh-word, and no subject-aux inversion!)

So in summary, "what did you say?" is a question, whereas "what you said" is a special kind of sentence called a nominal clause. Both are related together because they are connected to the same subject-verb-object "mother" sentence "you said what". The question is made by a question-forming process (subject-aux inversion, do affixing), and then a wh-movement (the wh-word moves to the front). The nominal clause is made just by wh-movement alone.

4

The first sentence is asking how two people guessed about a person you wanted.
The second is a clause, not a complete sentence. The complete sentence could be:

How you and mom guessed I wanted Agnes is still a mystery, for me.

I wonder how you and mom guessed I wanted Agnes.

I am still wondering how you and mom guessed I wanted Agnes.

I will never understand how you and mom guessed I wanted Agnes.

2

First of all, did + present tense is the same as past tense of the verb. Here are the three forms of the past simple:

Positive: You said it.

Negative: You did not say it. = You didn't say it.

Question: Did you say it?, When did you say it?

About your examples,

What did you say?

is a question. It can stand on its own.

what you said

is usually a part of a sentence. For example, "I want to know what you said" or "Can you please repeat what you said?"

The same with the other pair:

How did you and Mum guess I wanted Agnes?

does not need anything added to it, it is a complete question.

how you and Mum guessed I wanted Agnes

could be part of the sentence "I wonder how you and mum guessed I wanted Agnes".

-1

"Did" + [present tense verb] can be used in a statement, but should only be used when you want to sound thoughtful:

Person A: You know, Sally learnt that her boyfriend was cheating on her at the party.

Person B: Now that you mention it, I did think there was something strange about her behavior.

This construction is suggestive of a question, and so sounds thoughtful. It evokes the sense that the speaker is pondering the significance of the event.

This is really a point of style rather than grammar. The sentence "I did go to the grocery store" is grammatical, but less appropriate than "I went to the grocery store" when your intention is merely to report what happened.

  • 1
    Can you expand on the "why" of your answer? Please keep in mind, Stack Exchange is all about answers that will help future visitors, not just the person who asked the question. Telling people "why" as well as "what" helps these future visitors apply the knowledge here to their own personal situations. – Jonathan Garber Oct 8 '13 at 20:59

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