A2 如果不是
used to say what the situation will be if something does not happen
I hope to see you there but, if not, I'll call you. 我希望在那里能见到你，如果没有的话，我会给你打电话的。
If they have any mangoes, get a couple and if not, I'll pick some up tomorrow.
Obviously it would be great if Sam could drive us there, but if not, we can just get the train.
Weather permitting, we'll have the party outdoors. But if not, we'll take it indoors.
I hope to speak to Isabel after the meeting this morning but if not, I'll catch her tomorrow.
See also: not