Float and double problem in overlaoding

Question

#include <iostream>
using namespace std;
void sum(double a){
cout<< "it was a float";
}
void sum(int u){
cout<< "it was a int";
}
int main() {
sum(2);
sum(2.1);
return 0;
}

In this code when I Interchange the 'double a' to 'float a' in the first function it raises an error but according to lessons it should work
I don't understand whats happening
I guess float and double should behave similarly

(Try running the code in c++ by changing the float to double and vice versa to get an idea of what I am talking)

Answer 1

Then what's the difference between float and double
According to your explanation ~swim~ float is more similar to int tham it is to double.
Is it so??