Merge array

Hello,

My problem is that I want to merge 2 arrays to 1 array but I have errors when I build the program.

void can_merge_16_32(u16_t part_a, u16_t part_b)
{
    u32_t output = 0;
    u16_t i = 0;
    for( i = 0 ; i < 16 ; i++)
    {
        output[i] = part_a[i];
        output[i+16] = part_b[i];
    }

    return output;
}

src\\can.c(187): error: subscripted value is neither array nor pointer