✅ Simple Definition:

Recursion = Function calling itself repeatedly, with a smaller input every time, until it reaches a base case.

🔁 Real Life Example:

📦 Imagine ek box ke andar doosra box hai, fir uske andar ek aur...

Last me ek empty box milega — wahi hai base case.

Ab tum boxes ko pehle andar jaake, fir wapis nikalte ho — yahi hai recursion.

🔧 Syntax Example (C++):


void sayHello(int n){
    if(n == 0) return;             // base case
    cout << "Hello\n";
    sayHello(n - 1);               // recursive call
}

🔂 Example: Factorial using Recursion

    int factorial(int n){
    if(n == 0 || n == 1) return 1;    // base case
    return n * factorial(n - 1);      // recursive step
}

👉 factorial(5):


5 * factorial(4)
4 * factorial(3)
3 * factorial(2)
2 * factorial(1)
1 → base case = return 1

🧠 2 Important Parts of Recursion:

Part Explanation
✅ Base Case Jahan recursion rukti hai (warna infinite call ho jaayegi)
🔁 Recursive Case Jahan function khud ko call karta hai

❗ Why Base Case is Important?