Why is using "using namespace std;" considered bad practice in C++?

Hi everyone! I recently started learning C++ and in all tutorials I see `using namespace std;` written at the beginning of the code. It's convenient — you don't need to write `std::cout`, `std::vector`, and so on every time. But I've noticed that more experienced programmers often criticize this line and say it's better not to use it. My code is still small, and there don't seem to be any problems. But I want to understand what exactly the catch is. Here's a simple example that works for me: ```cpp #include #include using namespace std; int main() { vector numbers = {1, 2, 3}; cout << "Hello, world!" << endl; return 0; } ``` Why do some people consider this a problem? After all, the code becomes shorter and more readable. I've heard about "namespace pollution," but I don't fully understand how it can cause harm.