ZIP code

A ZIP code is a five-digit numeric code used by the United States Postal Service in sorting mail. The first digit indicates a group of states; the second and third, a region of a state or a large city; and the fourth and fifth, a small town, a delivery area in a larger town or city, a particular postal facility, or a particular large mail recipient. Extensions of the ZIP code include the nine-digit ZIP+4 code and the 11-digit ABC (Advanced Bar Coding) code.