Could you please answer with respect to B+ Trees.
Assume a leaf node has an order of 5.
Then the leaf node can have at-most 5 children pointers, which will be originating from the <key,pointer> pairs. Then the number of keys should also be 5. Assuming we are not counting the pointer to the next leaf.
If we count the next leaf pointer, then the number of keys will be 4 and that means, number of pairs are 4 and the order of a leaf node is defined as number of key, pointer pairs. This contradicts to our original assumption of order as 5.