Why is deleting in a single linked list O(1)?

Question

I do not quiet understand why deleting at the end of a single linked list goes in O(1) time, as the wikipedia article says.

A single linked list consists out of node

Answer 1

O(1) simply means "constant cost". It does not mean 1 operation. It means "at most C" operations with C being fixed regardless of other parameters changing (such as list size). In fact, in the sometimes confusing world of big-Oh: O(1) == O(22).

By contrast deleting the whole list has O(n) cost, because the cost changes with the size (n) of the list.