used to show that something depends on something else
If it rains, we will stay inside.
如果下雨,我们就待在室内。
when something always happens
If you heat ice, it melts.
如果你加热冰,它就会融化。
used to talk about possibilities
I don't know if I should go.
我不知道我是否应该去。
used with feeling words
I wonder if you can help me.
我想知道你是否能帮助我。
used to say something is not important
If he is late, it's not a big problem.
如果他迟到,也不是什么大问题。
used to ask someone to think about something
If you consider the time, we should leave now.
如果你考虑时间,我们现在应该离开了。
used to show a small contrast
She is nice, if a bit shy.
她人很好,虽然有点害羞。
used to ask politely
If you would wait here, I will get help.
如果您能在这里等候,我会去寻求帮助。
used to suggest something politely
If I may suggest, we could try again.
如果我可以建议的话,我们可以再试一次。
something that might not happen
Winning is a big if, but we can hope.
获胜是个很大的未知数,但我们可以抱有希望。