Postal Code Glossary

Eircode

Ireland's 7-character alphanumeric postal code system launched in 2015, designed to identify every individual address in the country.

Forward Sortation Area

The first three characters of a Canadian postal code, indicating a geographic region used for initial mail sorting.

Military ZIP Code

Special ZIP codes using pseudo-state codes APO, FPO, and DPO to route mail to U.S. military installations and diplomatic posts worldwide.

PIN Code

Postal Index Number — India's 6-digit postal code system introduced in 1972 to identify post offices across the country.

PLZ

Postleitzahl — the 5-digit postal code system used in Germany and the standard abbreviation for postal codes in German-speaking countries.

PO Box ZIP Code

A ZIP code assigned exclusively to a range of Post Office Boxes at a particular USPS facility, separate from the street delivery ZIP code for the same area.

Postal Code

A series of letters, digits, or both used by postal services worldwide to sort and deliver mail to specific geographic areas.

Postcode

The term used in the United Kingdom, Australia, and several other countries for their alphanumeric or numeric postal code system.

Standard ZIP Code

The most common type of ZIP code, representing a geographic delivery area served by regular USPS mail carriers and associated with residential and business addresses.

Unique ZIP Code

A ZIP code assigned exclusively to a single organization or entity that receives a high volume of mail, such as a government agency or large corporation.

ZIP+4 Code

An extended 9-digit ZIP code in the format 5+4 that identifies a more precise delivery point, such as a city block, building floor, or individual high-volume receiver.

ZIP Code

Zone Improvement Plan code — a 5-digit postal code used by the United States Postal Service (USPS) to identify delivery areas.

ZIP Code Tabulation Area

A statistical geographic entity created by the U.S. Census Bureau to approximate ZIP code delivery areas for demographic analysis.

Attention Line

An address line directing mail to a specific individual or department within an organization, placed above the organization name in USPS addressing format.

CASS Certification

Coding Accuracy Support System — a USPS program that certifies address-matching software to ensure it assigns correct ZIP+4 codes and delivery point codes.

City/Municipality

The city, town, or municipality component of a mailing address, which must match the USPS-recognized name for the delivery ZIP code.

County

An administrative subdivision of a state used for local government, identified in postal data by a FIPS county code but not part of the mailing address itself.

Delivery Point

The specific location where a mail carrier deposits mail for a recipient, identified by a unique 2-digit code appended to the ZIP+4 to form an 11-digit delivery point code.

DPID

Delivery Point Identifier — an 8-digit code used by Australia Post to uniquely identify every delivery point in Australia.

Last Line

The final line of a mailing address containing the city, state, and ZIP code, which the USPS uses as the primary field for initial mail routing.

PO Box

A locked, numbered mailbox at a post office where the recipient collects mail rather than receiving carrier delivery to a physical street address.

Rural Route

A historical addressing system for mail delivery in rural areas of the United States, largely replaced by 911 street addresses but still recognized by the USPS.

State/Province Code

A standardized abbreviation identifying a state, territory, or province within a country's mailing address system.

Street Address

The primary line of a mailing address that identifies a specific building or location on a named street, typically including a house number and street name.

Suite/Unit Number

A secondary address element that identifies a specific unit within a multi-tenant building, such as an apartment, suite, floor, or room.

Census Block

The smallest geographic unit used by the Census Bureau, typically bounded by streets, streams, or other visible features, for which only total-population counts are published.

Census Block Group

A subdivision of a Census tract containing between 600 and 3,000 people, the smallest geographic unit for which the Census Bureau publishes sample (survey) data.

Census Designated Place

An unincorporated community identified by the Census Bureau for statistical purposes, providing data for settled areas that lack a municipal government.

Census Tract

A small, relatively stable geographic subdivision of a county designed by the Census Bureau to contain approximately 4,000 people for demographic data collection.

Congressional District

One of 435 geographic divisions of the United States, each represented by a member of the U.S. House of Representatives.

Core-Based Statistical Area

A geographic region defined by the Office of Management and Budget (OMB) consisting of one or more counties anchored by an urban center of at least 10,000 people.

County Subdivision

A geographic subdivision of a county recognized by the Census Bureau, including townships, towns, election precincts, and minor civil divisions.

FIPS Code

Federal Information Processing Standard code — a numeric identifier assigned by the U.S. government to states, counties, and other geographic entities for use in data processing.

Metropolitan Statistical Area

A CBSA anchored by an urban area of at least 50,000 people, encompassing the core county and economically linked surrounding counties.

School District

A special-purpose government entity that administers public schools within a defined geographic boundary, tracked by the Census Bureau in relation to ZIP codes.

Urban Area

A densely settled geographic area defined by the Census Bureau based on population density thresholds, used to classify territory as urban or rural.

Urban Cluster

A Census-defined densely settled area with a population between 2,500 and 49,999, representing small cities and large towns.

Urbanized Area

A Census-defined densely settled area with a population of 50,000 or more, typically centered on a major city and its surrounding suburbs.

Area Distribution Center

A USPS facility that consolidates and distributes mail within a geographic region, operating between Network Distribution Centers and local post offices in the processing hierarchy.

Bulk Mail

Large-volume mailings sent at discounted USPS rates under a bulk mail permit, requiring presorting by ZIP code and meeting minimum piece counts.

Carrier Route

A specific path assigned to a USPS mail carrier within a ZIP code, covering a defined set of delivery points that the carrier visits in sequence.

Certified Mail

A USPS service that provides the sender with proof of mailing and electronic delivery confirmation, commonly used for legal and official correspondence.

Delivery Point Barcode

A barcode printed on a mail piece that encodes the ZIP+4 code plus a 2-digit delivery point suffix, enabling automated sorting to the individual delivery location.

Intelligent Mail Barcode

A 65-bar barcode used by the USPS since 2013 that encodes delivery point information, mail class, sender ID, and tracking data in a single symbology.

Last Mile Delivery

The final leg of the delivery process from the local post office or distribution hub to the recipient's mailbox or door.

Mail Processing Equipment

Automated machinery used by the USPS to sort, face, cancel, and sequence mail based on barcodes, OCR, and other recognition technologies.

Network Distribution Center

A large USPS facility that serves as a regional hub for sorting and transferring mail between Sectional Center Facilities across multiple states.

Parcel Select

A USPS ground shipping service for commercial mailers sending large volumes of parcels, offering lower rates in exchange for destination entry and longer delivery times.

Priority Mail

A USPS service offering 1-3 day delivery for packages and thick envelopes, with free packaging supplies, tracking, and up to $100 of included insurance.

Sectional Center Facility

A USPS mail processing plant that serves as the primary sorting hub for a group of ZIP codes sharing the same first three digits (the 3-digit prefix).

Age Distribution

The breakdown of a ZIP code's population by age groups, including median age and percentages in ranges such as under 18, 18-64, and 65 and older.

Commute Time

The average or median travel time in minutes that workers in a ZIP code spend commuting from home to work, reported by the American Community Survey.

Educational Attainment

The distribution of highest education levels completed by residents of a ZIP code, from less than high school to graduate or professional degrees.

Housing Units

The total count of houses, apartments, condos, mobile homes, and other separate living quarters in a ZIP code, whether occupied or vacant.

Land Area

The total dry-land surface area of a ZIP code or ZCTA, measured in square miles or square kilometers, excluding inland water bodies.

Median Home Value

The midpoint value of owner-occupied homes in a ZIP code, as estimated by the Census Bureau's American Community Survey.

Median Household Income

The income level at which half of households in a ZIP code earn more and half earn less, a key indicator of an area's economic status.

Owner-Occupied Housing

Housing units in a ZIP code where the occupant owns the property, as distinguished from renter-occupied units, expressed as a count or percentage.

Per Capita Income

Total personal income earned by all residents of a ZIP code divided by the total population, including non-earners such as children and retirees.

Population Density

The number of people per unit of land area (typically per square mile or square kilometer), used to classify ZIP codes as urban, suburban, or rural.

Poverty Rate

The percentage of individuals or families in a ZIP code living below the federal poverty line, as estimated by the American Community Survey.

Renter-Occupied Housing

Housing units in a ZIP code occupied by tenants who pay rent, including apartments, rented houses, and other leased dwelling units.

Water Area

The total surface area of inland water bodies (lakes, rivers, reservoirs) within a ZIP code or ZCTA boundary.

ACS (Address Change Service)

A USPS service that provides mailers with electronic notifications when mail is forwarded, returned, or undeliverable due to an address change.

Address Standardization

The process of reformatting a mailing address to conform to USPS addressing standards, including approved abbreviations, directionals, and correct ZIP+4 assignment.

CASS Certification Process

The formal USPS testing procedure that software vendors must pass to certify their address-matching products for use in qualifying mailings for automation discounts.

DPV

Delivery Point Validation — a USPS dataset that confirms whether a specific address (down to the suite or apartment level) is a valid, active delivery point that receives mail.

eLOT

Enhanced Line-of-Travel — a USPS sequencing system that assigns a sort order to addresses within a carrier route based on the carrier's actual delivery path.

Geocoding

The process of converting a street address or place name into geographic coordinates (latitude and longitude) for mapping and spatial analysis.

LACSLink

Locatable Address Conversion System — a USPS database that converts rural-style addresses (RR, HC) to their new 911 street addresses.

NCOA

National Change of Address — a USPS database containing 48 months of address change records, used to update mailing lists with current addresses.

PostalOne!

The USPS electronic documentation system that commercial mailers use to submit mailing statements, postage payment, and qualification reports for bulk mailings.

Reverse Geocoding

The process of converting geographic coordinates (latitude and longitude) into a human-readable address, place name, or ZIP code.

SuiteLink

A USPS database that appends secondary address information (suite, floor, or department numbers) to business addresses that are missing this detail.

USPS Web Tools API

A set of free APIs provided by the United States Postal Service for address validation, ZIP code lookup, rate calculation, and package tracking.