Perhaps specific context is required but what is the real meaning behind this
phrase?
CC BY-SA 4.0
2020-11-07T14:29:56.083
82510
2020-11-08T02:45:58.203
40711
question
phrases
What does 決まってんだろう imply?
決まる means "to be settled" or "to be decided", and 決まっている means "has been
(already) settled". But as a set phrase, (～に)決まっている also means "it goes
without saying ～", "needless to say" or "certainly (although there is no
direct evidence/guarantee)". See [JLPT N2 Grammar:
に決まっている](https://jlptsensei.com/learn-japanese-
grammar/%E3%81%AB%E6%B1%BA%E3%81%BE%E3%81%A3%E3%81%A6%E3%81%84%E3%82%8B-ni-
kimatte-iru-meaning/)

By extension, when used as the reply to a question, 決まっているだろう/決まっているでしょう
effectively sounds like "Why ask?" or "Of course, ～" or sometimes even "That's
a stupid question". You can think of this as a set phrase to memorize.

決まってんだろう is a contraction of 決まっているだろう:

  * 決まっ **ている** だろう: (literally) "It has been settled, hasn't it?"
  * 決まっ **てる** だろう: ("teiru → teru" contraction described [here](https://japanese.stackexchange.com/a/18159/5010))
  * 決まっ **てん** だろう: ("ru → n" contraction)
CC BY-SA 4.0
2020-11-08T02:40:50.960
82515
2020-11-08T02:45:58.203
2020-11-08T02:45:58.203
816
5010
82510
answer