in confidence
咱们（或你我）私下说说
just between you and me, I don't think it was going to happen.
只是咱们私下说说，我认为这事不会发生的。
in the intervals between other actions
在间歇期间
In the strictest confidence.
你知我知，天知地知：表示非常信任
In an intermediate situation
在中间的状况
My roommates disagreed and I was caught in between.
我的室友不同意，我被夹在中间进退两难
During an intervening period; in the meantime
穿插着；同时：在其间的一段时期；同时
has written several books and teaches in between times.
在写书的同时也教书