"Why can't I see?" or "Why I can't see?"?

Why can't I see?

is a question.

Why I can't see

may be used in a title.

He knows why I can't see

is a statement.

why

1. Used in questions to ask the reason for or purpose of sth

2. Used to give or talk about a reason

3. Used in questions to suggest that it is not necessary to do sth

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The sentence

Why can't I see?

is more applicable when you are asking a question [1].

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The sentence

Why I can't see?

will be considered grammatically wrong in this case.

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However, if you want to talk about the reason behind it (make a statement[2] ), you can use

why I can't see

in a sentence like this:

That's why I can't see.

instead of

That's why can't I see. (grammatically wrong)

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But in some countries like Singapore, Hong Kong, etc,

it is alright to ask a question both way.

Why can't I see?

This is perfectly complete meaningful sentence and interrogative sentence.

Why I can't see?

We can't use it in interrogative sentence. It is incomplete sentence.

He doesn't know why i can't see.

It is completely meaningful sentence and not interrogative sentence.

Doesn't he know why i can't see?

It is completely meaningful sentence and interrogative sentence.

Question : Why can't I see ? For EG. This is a question that is genreally asked when you are able to see.. Statement : Why I can't See. For EG. This is a statement when you somebody is forcing you to not see anything.