diff --git a/src/c/funktionen.h b/src/c/funktionen.h
index e8b0d08..7a45053 100644
--- a/src/c/funktionen.h
+++ b/src/c/funktionen.h
@@ -25,4 +25,7 @@ float naturalLogarithm(float x);
 // Function to calculate the exponentiation of a number to the power of another number
 float power(float x, float y);
 
+// Function to calculate the factorial of a number
+int factorial(int x);
+
 #endif
\ No newline at end of file