[Serie: All About Japanese Particles]
1. Following da or ka, indicates an informal question. Used mostly by men.
どうして新宿まで行ったんだい。
Dō shite Shinjuku made itta-n dai.
Why’d you go as far as [all the way to] Shinjuku?
昨日どこで飲んだんだい。
Kinō doko de nonda-n dai.
Where’d you go drinking yesterday?
またアメリカに主張かい、大変だな。
Mata America ni shuchō kai, taihen da na.
Off to the U.S on business again? Hang in there.
あの人、元気だったかい。
Ano hito, genki datta kai.
How was she? / How’s she getting along?
– Source: All about particles – A handbook of Japanese function words –