1An adverb used to express surprise or emphasis (as in "what/how ..."); can mean "how" or "what" in exclamations or questions.
何と大きな家だろう。
What a huge house!
何と書けばいいかわからない。
I don't know what I should write.
彼は何と答えたの？
What did he answer?
2An exclamatory adverb expressing surprise, admiration, or emphasis ("what...!"/"how...!").
なんと素晴らしい演奏だったのだろう。
What a wonderful performance that was!
なんと優しい人なんだろう。
How kind a person he is!
なんと美しい景色だろう。
What a beautiful view!
3Used to indicate surprise or unexpectedness ("surprisingly", "to my amazement", "believe it or not").
なんと彼はその会社の社長だった。
To my surprise, he was the president of that company.
なんと、あの古い店がまだ営業していた。
Surprisingly, that old shop was still open.
なんと彼女が合格していたとは信じられない。
I can't believe she passed, of all things.
4An interjection expressing surprise or admiration ("oh my", "wow", "well!"), often used alone.
「彼が優勝したよ」「なんと！」
"He won the championship." "Wow!"
なんと！それは予想外だ。
Oh my! That's unexpected.
なんと、こんなところで会うとは。
Well well, to meet you here of all places!
5An interjection used to open a remark while seeking someone's agreement or confirmation ("well, ..."; "so, ..."), often softening an invitation or proposal.
なんと、一つ景気づけに乾杯といこうじゃないか。
Well then, how about a toast to lift our spirits!
なんと、これで手を打とうではないか。
Well, why don't we settle on this, then?
なんと、久しぶりに一杯どうだ。
So, how about a drink together, it's been a while?