Structure raises linker exception multiple definition of

[Vila]

As I read from some online examples structures should work like this:

struct nameOfStruct
{
int myMember1;
short myMember2;
};

int main()
{
nameOfStruct myInstance;
myInstance.myMember = 444;
return 1;
}

This code doesn't link good:
Undefined reference to nameOfStruct::myMember1
First question, why?

So i found some example and "repaired" my code:

struct nameOfStruct
{
int myMember1;
short myMember2;
};

int nameOfStruct::myMember1;

int main()
{
nameOfStruct myInstance;
myInstance.myMember = 444;
return 1;
}

Now code compiles well.
As my application developed, I came to the point when I must make this type (structure) visible to multiple units. So i tried to do this:

//Structures.h
struct nameOfStruct
{
int myMember1;
short myMember2;
};

int nameOfStruct::myMember1;

//Functions.h
void Function1(nameOfStruct myStructArgument);

//Functions.cpp
#include "Structures.h"

void Function1(nameOfStruct myStructArgument)
{
//code
}

//Main.cpp
#include "Structures.h"
#include "Functions.h"

int main()
{
nameOfStruct myInstance;
Functions1(myInstance);
myInstance.myMember = 444;
return 1;
}

And so i get linker error: Multiple definition of nameOfStruct::myMember.
Second question, why?

Thanks for help