"How so sure?" As a complete question



Can I say "How so sure?" to question the validity of a claim. For example:

A) They will lose.

B) How so sure?

Is it grammatical? If yes then is it common and natural?


Posted 2014-05-28T18:54:13.663


4I think it's more natural for B to say, "Are you sure?", "Why are you so sure?", "Why do you feel so sure?", or "How can you be so sure?" – Damkerng T. – 2014-05-28T19:30:32.313


or perhaps: how come you are so sure?

– Nico – 2014-05-28T19:51:54.727

1I think "How so sure?" is either a very limited-currency non-standard version of "Why [are you] so sure?", or more likely just an inappropriate form which is more likely to occur to non-native speakers (who it seems to me often conflate how and why). Another "idiomatically normal" response in OP's context might be "You're sure? How's that?" (i.e. - "How does that come about?"). – FumbleFingers Reinstate Monica – 2014-05-28T20:54:17.887

2The most common phrase I hear is "What makes you so sure?". – Casey Kuball – 2014-05-28T21:14:33.013



"Why so sure?" is the form of the question that you're looking for - it is a common structure.

*"How so sure?" is incorrect (though obviously both "How sure?" and "How (come) are you so sure?" are OK - though their meanings are different).

Unless of course you want to know something still else - "How sure are you?" - meaning, are you very sure, or just a little bit sure? (an oxymoron, since certainty would seem to be a binary concept, and yet we can be "sure" and "very sure"...)

Alicja Z

Posted 2014-05-28T18:54:13.663

Reputation: 1 672

Thank you very much :) I am a little confused. Why is it correct to say "Why so sure" but incorrect to say "How so sure?" and Why inclusion of "so" makes the question incorrect. I've gotten my answer but If you would, Please help me to understand this too. – None – 2014-05-28T20:12:04.693

1@GATA Actually, I've been wondering that myself... Better yet, "Why sure?" would also be wrong in this meaning. I'll ask over at English.SE - unless you would like to? – Alicja Z – 2014-05-28T20:17:52.197

I don't like to trouble you again but if you are as curious as I am then I think I would benefit more if you ask it. My English is not good enough for English.SE :) – None – 2014-05-28T20:34:09.560


@GATA Ok, posted here... Though from what you've written here so far, it looks like your English is pretty good :)

– Alicja Z – 2014-05-28T21:03:05.720

2@GATA: "Why so sure?" is a common idiom, despite not being formally correct. "How so sure?" is not. There's no good reason, that's just the way it is. – keshlam – 2014-05-28T21:15:01.920

1@GATA Since you were the co-author of the question on English.SE in a way, does Jon's answer there satisfy you? – Alicja Z – 2014-05-28T22:42:48.160

1How sure? means how sure are you?, not how are you sure? – Esoteric Screen Name – 2014-05-29T01:58:40.597

@AlicjaZ YES :) It was clear. Thank you for everything. and also Thank you all other contributors. – None – 2014-05-29T04:15:52.147

@EsotericScreenName Yes, you're correct - my point was only that they're both correct sentences, not that they mean the same thing. – Alicja Z – 2014-05-30T11:54:18.483

@Alicja may I suggest changing the structure of your answer then? Putting it next two other sentences that mean something else rather than in the paragraph which discusses the meaning might be taken otherwise. – Esoteric Screen Name – 2014-05-30T12:45:39.040

@EsotericScreenName Better? – Alicja Z – 2014-05-30T16:58:09.640

Native English speaker here. I feel 'Why so sure?' is slang and 'overly-friendly' between random adults. This is the sort of clipped language I would use around small children (like 'Billy wants a drink?'/'Billy drink?' addressed to Billy) – Merk – 2014-05-30T23:39:13.943

@Merk Yes, it's on the friendly, informal side of things (I wouldn't use it with a professor, for instance), but I wouldn't go so far as to call it slang. It's commonly used (both by itself and followed by something, eg. Why so sure he won't come?), understood by all native speakers, and is nowhere near the 'Billy drink?' example (which is completely ungrammatical) in terms of "level" of language. (also a native speaker) – Alicja Z – 2014-06-01T21:06:41.097


You don't really have a verb in that sentence. You would probably say "How are you so sure?"


Posted 2014-05-28T18:54:13.663

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