This question already has an answer here:

I don't know the difference between how we make a car and how do we make a car.

I searched on the internet; there are examples for both but I do not understand in which cases they would each be used.

marked as duplicate by TimLymington, user66974, Ronan, FumbleFingers, Robusto Aug 8 '14 at 18:57

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  • 5
    That question would be better suited for the English Language Learners site. – Alex W Aug 7 '14 at 18:02
  • 4
    In addition to the fact that, as @AlexW says, this is the wrong site, you'll also need to provide some more context. Did you see these sentences somewhere? Do you want to use them in a particular context and not know which to use? – GalacticCowboy Aug 7 '14 at 18:21
  • I favour leaving this question here, as I'm not certain we have something similar in ELU. An ELL question is at “Do in WH- questions” and its linked duplicate. – Andrew Leach Aug 7 '14 at 18:28
  1. How we make a car is not a sentence; it's a subordinate clause. It's certainly not a question.

  2. How do we make a car is a sentence, and a question (if it has question intonation, i.e. ?)

Both of them come from the structure

  • We make a car Indef_manner

where Indef_manner means some indefinite manner or way (of making a car).
Indef_manner is what gets turned into how, the interrogative pronoun for expressions of
manner and means, just as when is the relative/interrogative pronoun for expressions of time.

The difference between the two examples that come from this structure is that
  the first sentence has a pronoun in front, but no other change, while
  the second sentence has a pronoun in front, and an auxiliary verb before the subject.

Putting the verb before the subject is the mark of a question. So the second one is a question.
The first one is an Embedded Question, or Free Relative, which is a type of complement clause.
Embedded questions do not invert auxiliary verbs with the subject.

  • How can they make this car so ugly?
    (full sentence; question; auxiliary verb can precedes subject they)
  • I don't know how they can make this car so ugly.
    (embedded question object complement of know; subject they precedes auxiliary verb can)
  • 1
    Or could be a clumsy exclamative sentence! – Araucaria Sep 12 '14 at 14:05

When an interrogative pronoun is the subject of a sentence, do is not required. As interrogative pronouns normally need to be at the start of the sentence, subject–verb inversion doesn’t happen either.

He makes the car. (Statement; “he” is the subject)
Who makes the car? (Question: “who” is the subject)

When the question does not have an interrogative pronoun as the subject, do or another modal verb is required. That verb precedes its subject.

How do we make the car? (“We” is the subject and “how” is an interrogative adverb)

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