A code which was established by the United States Postal Service, for the purposes of identifying a location and routing the mail to that location. A zip code was originally 5 digits long, and now has been expanded to 9 digits for more detailed identification. The 5 digit zip code is still sufficient for sending all items of mail; the 9 digit zip code is used primarily by businesses as they sometimes get a discount for doing so. Zip code stands for ‘Zoning Improvement Plan' code.
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