multiple definition of function in C : I'm writing a functions for my current project.

Right now, I have a Countries.h header.

when i try to complie this is the error that I get:
 
CMakeFiles/untitled2.dir/Countries.c.o: In function `addCountry':
/home/ise/CLionProjects/untitled2/Countries.c:36: multiple definition of `addCountry'
CMakeFiles/untitled2.dir/main.c.o:/home/ise/CLionProjects/untitled2/Countries.c:36: first defined here
collect2: error: ld returned 1 exit status
CMakeFiles/untitled2.dir/build.make:98: recipe for target 'untitled2' failed
make[3]: *** [untitled2] Error 1
CMakeFiles/Makefile2:72: recipe for target 'CMakeFiles/untitled2.dir/all' failed
make[2]: *** [CMakeFiles/untitled2.dir/all] Error 2
CMakeFiles/Makefile2:84: recipe for target 'CMakeFiles/untitled2.dir/rule' failed
make[1]: *** [CMakeFiles/untitled2.dir/rule] Error 2
Makefile:118: recipe for target 'untitled2' failed
make: *** [untitled2] Error 2


I tried a lot of things but nothing worked

