Level 4 · Upper Intermediate
Otherwise: 要不然 and 否则
A，要不然 / 否则 + B · Traditional: A，要不然 / 否則 + B
要不然 (yàoburán) opens the bad thing that will happen if A doesn't get done: 快一点，要不然我们要迟到了 "hurry up, otherwise we'll be late". 否则 (fǒuzé) means the same but sounds a bit more formal and written.
The "otherwise" clause describes a result that hasn't happened yet, so it usually carries 会, 要…了, or 就: 要不然你会感冒 "otherwise you'll catch a cold". A bare verb after 要不然 sounds unfinished.
Examples
快一点，要不然我们要迟到了。
快一點，要不然我們要遲到了。
kuài yī diǎn yào bù rán wǒ men yào chí dào le
Hurry up, otherwise we're going to be late.
多穿一点，要不然你会感冒。
多穿一點，要不然你會感冒。
duō chuān yī diǎn yào bù rán nǐ huì gǎn mào
Put on more clothes, otherwise you'll catch a cold.
我们现在就走吧，否则就太晚了。
我們現在就走吧，否則就太晚了。
wǒ men xiàn zài jiù zǒu ba fǒu zé jiù tài wǎn le
Let's leave right now, otherwise it'll be too late.
快给妈妈打电话，要不然她会担心。
快給媽媽打電話，要不然她會擔心。
kuài gěi mā ma dǎ diàn huà yào bù rán tā huì dān xīn
Call mom quickly, otherwise she'll worry.
Common mistakes
✗ 快一点，要不然迟到。
✓ 快一点，要不然我们要迟到了。
The clause after 要不然 states a future result, so it wants 会 or 要…了.
Related grammar points
See it in a story
Read this pattern in context: Give Up Halfway — free graded stories with tap-to-reveal pinyin and translations.
