if not

Từ điển Oxford Advanced Learner 8th

if ˈnot idiom
1. used to introduce a different suggestion, after a sentence with if
• I'll go if you're going. If not (= if you are not) I'd rather stay at home.
2. used after a yes/no question to say what will or should happen if the answer is ‘no’
• Are you ready? If not, I'm going without you.
• Do you want that cake? If not, I'll have it.
3. used to suggest that sth may be even larger, more important, etc. than was first stated
• They cost thousands if not millions of pounds to build.
Main entry: ↑if_idiom