diff --git a/src/c/funktionen.h b/src/c/funktionen.h
index fa73c03..1401fde 100644
--- a/src/c/funktionen.h
+++ b/src/c/funktionen.h
@@ -19,4 +19,7 @@ float absolute(float x);
 // Function to calculate the logarithm (base 10) of a number
 float logarithm(float x);
 
+// Function to calculate the natural logarithm (base e) of a number
+float naturalLogarithm(float x);
+
 #endif
\ No newline at end of file