defining unused parameters in C

I need to use pthreat but I dont need to pass any argument to the function. Therefore, I pass NULL to the function on pthread_create. I have 7 pthreads, so gcc compiler warns me that I have 7 unsued parameters. How can I define these 7 parameters as unused in C programming? If I do not define these parameters as unused, would it cause any problem? Thank you in advance for the responses.

void *timer1_function(void * parameter1){
//<statement>
}

int main(int argc,char *argv[]){
  int thread_check1;
  pthread_t timer1;
  thread_check1 = pthread_create( &timer1, NULL, timer1_function,  NULL);
    if(thread_check1 !=0){
        perror("thread creation failed");
        exit(EXIT_FAILURE);
    }
while(1){}
return 0;
}