Difference between 忘れてた and 忘れちゃった


Who knows the difference between 忘れてた and 忘れちゃった? In what kind of situations
you use each of those?




ちゃう is the shortened form of
[ちまう](http://dictionary.goo.ne.jp/leaf/jn2/142344/m0u/). Which is the
shortened version of
[〜てしまう](http://dictionary.goo.ne.jp/leaf/jn2/100617/m0u/).

In this case, ちゃう represents, _" Implying that something unexpected
happened"_.

So if you say 忘れてた it means, "I forgot". But わすれちゃった means "I forgot having
unexpected consequences".

In my experience, using ～てしまう or ～ちゃう is more of a "whoops!" sort of comment,
whereas 忘れてた is more of a statement of fact. "Do you remember coming here as a
child?" would be more of the latter, while waiting in line for a baseball game
and realizing you forgot the tickets would be more of the former
「チケットを忘れちゃった！」

In general, the use of either ～ちゃう or ～てしまう when referring to a personal
screw-up is incredibly casual and not appropriate for work settings (you would
generally apologize first, as it comes off a bit too light-hearted and as if
you don't take the mistake seriously).

