What Do the Letters Z-I-P Stand for in the Words Zip Code?
The “ZIP” in “ZIP code” seems to describe the speed with which mail is delivered across the country. In fact, it is a word formed by joining the first letters of the words “Zone Improvement Plan.” Such made-up words are known as “acronyms.”
An acronym is a word formed from the first letter or letters of each word in a compound term. “Scuba,” for example, is an acronym for “self-contained underwater breathing apparatus.” Another well-known acronym is NASA, which stands for “National Aeronautics and Space Administration.”
However, the USPS intentionally chose the acronym to indicate that mail travels more quickly when senders mark the postal code on their packages and envelopes. The general system of ZIP codes used today was implemented in 1963. Prior to this system, the USPS used a system of postal zones, which was only applicable to large cities. This is where the “improvement” part comes into play.
The basic ZIP code has five digits. The first three digits refer to a sectional center facility (or SCF), what is basically a network of super post offices. All of the post offices that have those three digits in their ZIP code have their mail sorted and processed by the same SCF. The last two numbers designate the specific post office within an SCF’s territory.
In the 1980s a new system was introduced called ZIP+4. Four additional digits (with a hyphen) were added to the basic code. This allowed senders to indicate an even more precise location, such as a particular block or apartment building. The rise in post office boxes also made this greater level of precision necessary.
Here’s one more postal term to file away: Postnet. The Postnet is a ZIP code translated into a barcode and printed on a piece of mail. The Postnet makes it more efficient for automated machines to sort mail.