Circuit completion : is it necessary?
Wait, we say something is charged if it has more positively charged particles than negatively charged ones or vice versa. If we connect two oppositely charged bodies, by say a wire, the charge will be transferred, to make the system more uniformly charged, if not neutral.
So, actually, the negative mobile particles, electrons for example, get transfered to the wire, making it negatively charged, and then to the positive body(or even a neutral one) making the system more electrically stable.
Indicating that the wire is charged at some unit time.