I don't know if not meaning in this sentence

Hello.
I read a book.
I saw a sentence that "we call the pair a breakpoint if not".
I wonder that the "if not" meaning.

Would you please explain what is this. ( what dose it mean )

Thanks

Hello 보국,

It is quite difficult to work out the full meaning without more context. (Surrounding words.) Looking at the sentence and from research I believe that they are talking about 2 numbers and if they are adjacent ie next to each other they are an adjacency and if they are not next to each other (ie not an adjacency) they are called a breakpoint. (From Computational Physics By D.k. Jha - page 263)

So 'if not' here means if the previous statement is not true.

Hope this helps

Bob