"How come?" means "Why?" right?

Is it possible to replace "Why" in a sentence with "How come"?

Cinese tradizionale (Hong Kong)

It depends on a sentence. Pls give me some examples.

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Gejemica

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Inglese (Stati Uniti)

You cannot simply replace "why" with "how come" because if you use "how come", you use the positive sentence structure:

He is here. - positive sentence

Why is he here? - question with why
How come he is here? - question with how come

You know how to do that. -positive sentence

Why do you know how to do that?
How come you know how to do that?

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Giapponese

Thanks for answering!
So I can say "How come" followed by a normal (affirmative) sentence.
Can I say "How come you don't know him?"?
(Should I use only one question mark?)

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I use 'how come' and 'why' in the same way, although why does sound better and is a safer choice to say yourself

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Giapponese

@Annie1998
"why" sounds better? Why is that?

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@ilikeplants I consider 'how come' to be a very casual, informal or conversational way of saying why. If I were writing an essay for school or a formal letter, I would always use why.

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Giapponese

@Annie1998 I understand. I think what you've explained is the reason why I didn't remember seeing sentences like "How come you like the picture?" often.

Does "How come" only mean "Why do(es) ~?"
Can a sentence like "How come you sing so well?" mean "Why can you ~ ?"?

Giapponese

@Gejemica I failed to mention you. Sorry!

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@ilikeplants No, it just means why. Another way it's used is that when someone says something, you could reply simply with 'how come?' meaning why, although this is informal. Yes, you can can say 'how come you sing so well?' and it makes sense. Some more examples of sentences are 'how come you like that band?', 'how come she didn't do that?', 'how come cats meow?', etc. It is used just in the place of why.
All of these examples are quite informal though, and I wouldn't really consider them proper written English. There'll be fine to use in conversation with people you're familiar with though. 'How come' is frequently used by British people, correctly or not.

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Giapponese

@Annie1998 OK. Thank you!
If "How come" only means "Why," should I say "How come you can sing so well?" to replace "Why can you sing so well?"? (tell me whether or not I should omit the last question mark) Or is the sentence less natural than when it doesn't have "can"?

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@ilikeplants you can say both 'how come you sing so well' and 'how come you can sing so well' but 'how come you can sing so well' is less informal and sounds better to me.

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@ilikeplants also the second question mark is correct, because your quotes (which were questions) were inside a question 😊

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Giapponese

@Annie1998 I'd have thought the opposite for both of them!
Thank you, your explanations are so helpful because they're what I'd never know if I didn't talk with a native speaker.

"How come can you sing so well?" is better and
Multiple question or exclamation marks are OK. I'll remember those.

But how about
"I said, 'This is so cool!'."
?
is the use and place of the period OK?
I'm asking this because I think you have to put everything inside the quotation marks in American English. So there'd be no period.
I want to learn both British English and American English.

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@ilikeplants Yes I think that would work, because the exclamation mark is part of the quote but the full stop is ending the sentence as a whole. That's how I would write it.

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