Can “How to” be a question?

Question

Can I use “How to” instead of “How do I” when I ask a question? And will it be grammatical?

I often notice some English learners use “How to” when they ask a question.

Answer 1

The usage of how to to ask a question is a direct translation from the learner's own language: it is not correct as a question in English. The expression is used in titles, for example "How to win friends and influence people"

In English, a how-question is formed by taking a normal sentence, making a question in the usual way (by applying subject-auxiliary inversion) and then adding how in front of it.

I get a visa
I do get a visa - add do because there is no auxiliary verb
Do I get a visa? - invert subject and auxiliary
How do I get a visa? - add how

Answer 2

Are you talking of asking some guy How do I kill an insect ?, versus How to kill an insect ? ? If so, I believe the latter is not grammatically correct.
I think How to is used more in titles and such (not in the question form), for example: How to kill all the insects in your house in less than 3 hours.

Answer 3

If you are asking the question directly to a person or group of people then

How do I feed a lion?

is grammatical. However we can also be making the point that it's a problem to do a task and say

Ah, but how to feed the lion? That's the question.

Here we are not explicitly asking a specific person for an answer, though in conversation we are open to receiving answers.

I suspect that these two cases are sometimes confused by non-native speakers.

Answer 4

The phrase "How to play tennis" is noun phrase. It does not contain a finite verb and is not a complete sentence. It is not a question. It means "the method of playing tennis"

Noun phrases are useful: They can be used, for example, as headings in a piece of writing. They are building blocks of complete sentences

He taught me how to play tennis.

This is a complete sentence with a subject, verb and two objects. It is not a question.

"How" can also be used in questions, but it needs the inverted verb to be a question.

How does he play tennis?

Answer 5

In English, whether something is a question or a statement can depend on its context or delivery.

For example:

1. Salesman: Hey, have I got a deal for you!
2. Customer: Really?
3. Salesman: Really!

Sentence 1 is worded in the form of a question ("Have I"), but the intent is to make a statement. Sentences 2 and 3 contain the same text, but #2 is a question while #3 is a statement.

"How to" can be used in a question, particularly when someone is asking a question of themselves (e.g. "How to win?"), but its natural function is to cue a reader to expect a heading or title (e.g. How to cook a potato).