error LNK2005 already defined in card.obj

this code gives me error LNK2005 Severity Code Description Project File Line Suppression State
Error LNK2005 getCardHolderName already defined in card.obj and
Severity Code Description Project File Line Suppression State
Error LNK1169 one or more multiply defined symbols found Payment_Application
what should I do ??

  //main.c
#include <stdio.h>
#include "STD_TYPES.h"
#include "card.c"

ST_cardData_t NewCustomer;

void main(void)
{
    uint8_t x;
    x=getCardHolderName(NewCustomer.cardHolderName);
    if (x == 0)
    {
        printf("Name is Valid");
    }
    else
    {
        printf("Name is Invalid");
    }
}

//card.h
#ifndef _CARD_H
#define _CARD_H

#include "STD_TYPES.h"

typedef struct ST_cardData_t
{
    uint8_t cardHolderName[25];
    uint8_t primaryAccountNumber[20];
    uint8_t cardExpirationDate[6];
}ST_cardData_t;


typedef enum EN_cardError_t
{
    OK, WRONG_NAME, WRONG_EXP_DATE, WRONG_PAN
}EN_cardError_t;

EN_cardError_t getCardHolderName(ST_cardData_t* cardData);
EN_cardError_t getCardExpiryDate(ST_cardData_t* cardData);
EN_cardError_t getCardPAN(ST_cardData_t* cardData);
#endif

//card.c
#include "card.h"
#include <stdio.h>
#include <string.h>
#include "STD_TYPES.h"

EN_cardError_t getCardHolderName(ST_cardData_t* cardData)
{
    uint8_t validity;
    printf("Please Enter The Card Holder Name (24 characters max - 20 characters min) : ");
    fflush(stdin);
    gets(cardData->cardHolderName);
    //scanf("%[^\n]s", cardData->cardHolderName);
    if ((strlen(cardData->cardHolderName) <= 24) && (strlen(cardData->cardHolderName) >= 20))
    {
        return OK;
    }
    else
    {
        return WRONG_NAME;
    }
}

>Solution :

#include "card.c"

It’s probably a better idea to include the header file rather than the C file.

The latter will cause duplicate symbols if you link the main object file and the card object file since main includes the exact same code as card (as a subset).