| HMB | Hudson Message Base |
| cea | County Education Authority |
| LSA | Local Security Authority |
| ISA | International Search Authority |
| MTA | Metropolitan Transportation Authority |
| NAPTR | Naming Authority Pointer |
| AHJ | Authority Having Jurisdiction [engl.] Kommunale Inspektoren |
| CA | Certification Authority [engl.] Berechtigte Stelle zur Bestätigung digitaler Schlüssel |
| CAA | Civil Aviation Authority [U.K.] London, http://www.caa.co.uk |
| KTA | Korean Telecommunication Authority |
| SOA | Start Of [zone of] Authority [DNS] |
| SAS | Signature Authority System |
| TVA | Tennessee Valley Authority |
| IBA | Independent Broadcasting Authority |
| TWA | Trans World Airlines Heute: American Airlines, http://www.aa.com/de |
| TCT | Trans Canada Trail ein Radfern- und Wanderweg, von der Ost- zur Westküste Kanadas |
| TPR | Trans Pacific Radio |
| TEE | Trans-Europ-Express vgl. http://www.tee-classics.ch |
| TAP | Trans Arabian Pipeline vgl. http://almashriq.hiof.no/lebanon/300/380/388/tapline/ |
| XMTR | "transmitter [das X steht für ""trans""] " |
| TVD | Trans Video Deutschland Renningen, http://www.tvd-online.de |
| TEL | Trans Europe Line Glasfasernetz zwischen West- und Osteuropa |
| XFER | "transfer [das X steht für ""trans""] " |
| TEN | Trans Europ Nacht Bahn |
| TCA | Trans - Canada Airlines Heute: Air Canada, http://www.aircanada.com |
| LEAF | Linking and Exploring Authority Files |
| FPHA | Federal Public Housing Authority |
| HEA | Health/Higher Education Authority |
| FLRA | Federal Labor Relations Authority |
| IANA | Internet Assigned Numbers Authority |
| FAID | Flash Authority Identification Data |
| A.D.E. | Atomic Energy Authority [engl.] Britische Atombehörde |
| AATA | Ann Arbor Transportation Authority [engl.] Ann Arbor, [MI], http://www.theride.org |
| AFI | Authority and Format Identifier [engl.] Teil der IDP im ATM-Standard |
| ARL | Authority Revocation List [engl.] |
| ASA | Advertising Standard Authority [engl.] Britische Behörde zur Überwachung der Werbung |
| AUC | Authentication/Authority Centre [engl.] |
| BAA | British Airport Authority [engl.] Britischer Flughafenverband |
| AAIC | Accounting Authority Identification Code Abrechnungskennung bei Gesprächsanmeldung über eine Küstenfunkstelle |
| BTA | British Tourist Authority [engl.] |
| TAPS | Trans Alaska Pipeline System Anchorage, http://www.alyeska-pipe.com |
| TAG | Trans Austria Gasleitung GmbH Wien, http://www.taggmbh.at |
| P6 | Trans Air [IATA-Airline-Code / USA] |
| TABD | Trans-Atlantic Business Dialogue Brüssel/ Washington, DC, http://www.tabd.com |
| TAT | Trans-Atlantic Telephone Cable vgl. http://www.iscpc.org/cabledb/atlan_page.htm |
| TEEM | Trans-Europ-Express-Marchandises |
| TENP | Trans-Europa-Naturgas-Pipeline Essen/ Mailand, [I] - vgl. http://www.dossenbach.de/pipeline-bau.htm |
| PCA | Policy Certification Authority [im Deutschen Forschungsnetz] Hamburg, http://www.dfn-pca.de |
| UKAEA | United Kingdom Atomic Energy Authority Culham, http://www.ukaea.org.uk |
| TAFTA | Trans-Atlantic Free Trade Area Transatlantische Freihandelszone |