不然

1. not so

♦ 其实~。 Actually this is not so.

2. (used at the beginning of a sentence to express disagreement) no

♦ ~, 事情没有那样简单。 No, it's not as simple as that.

3. or else; otherwise; if not

♦ 我得早点去, ~就赶不上火车了。 I've got to leave a bit early, otherwise I'll miss the train.