More conditions: 要不是, 否则, 不然, 万一, 假如, 除非

Beyond 如果

You know 如果…就 (Because, although, if: 因为…所以, 虽然…但是, 如果…就) and 只要/只有 (只要…就 and 只有…才: as long as, only if). These words add finer meanings.

要不是: if it hadn't been for

要不是 takes a real fact and imagines the opposite. The second clause says what would have happened, often with 就 or 早就.

• 要不是下雨，我们早就到了。If it hadn't been for the rain, we'd have arrived long ago.

否则 and 不然: otherwise

Both start the second clause: "do this, otherwise that". 不然 (or 要不然, 要不) is the everyday word; 否则 is common in writing and formal speech.

• 快点儿走吧，不然要迟到了。Let's hurry, or we'll be late.
• 申请表必须在周五前提交，否则不予受理。Applications must be submitted by Friday; otherwise they will not be accepted.

万一: just in case

万一 means "one chance in ten thousand": an unlikely possibility, usually an unwelcome one. It often ends with 呢 or 怎么办.

• 多带点儿钱，万一不够呢？Take a bit more money, in case it isn't enough.

假如 and 假设: suppose

假如 is a slightly more formal 如果, good for imagined situations. 假设 also means "assume" in an argument.

• 假如你是校长，你会怎么做？Suppose you were the head teacher: what would you do?

除非: two patterns, one meaning

• 除非 A，才 B: only if A, B. 除非你去，他才去。= He'll only go if you go.
• 除非 A，否则/不然 (不) B: unless A, not B. 除非你去，否则他不去。= Unless you go, he won't.

Both say the same thing. Watch the second clause: 才 with a positive, 否则 with a negative.

• 除非有特殊情况，他才会请假。He only takes leave in special circumstances.
• 除非你亲自去，否则他不会同意。Unless you go in person, he won't agree.

Common mistakes

• 要不是你帮我，我能完成。 → 要不是你帮我，我就完不成了。After 要不是, say what would have happened without the fact.
• 除非你去，他就去。 → 除非你去，他才去。除非 pairs with 才, not 就.
• 除非你去，否则他去。 → 否则他不去。After 否则 the outcome is the opposite, so it is usually negative.
• 万一明天天气很好，我们就去公园。 is odd: 万一 suggests something unlikely and usually unwelcome. For a neutral plan, use 如果.