| A. & C.P. | Anchors and Chains Proved |
| A.C. | Account Current |
| a.h. | after hatch |
| a.m. | ante meridiem |
| A.V. | Ad Valorem |
| A/C | Account, Altered Course |
| A/d | After date |
| A/or | And or |
| A/P | Additional Premium |
| A/S | After sight, Alongside |
| A1 | Top category or in "Good Condition" |
| AA | Always Afloat |
| Aa | Arrival After |
| AAIC | Accounting Authority Identification Code |
| AAR | Against All Risks (insurance clause). |
| ABI | U.S. Customs' "Automated Broker Interface," by which brokers file importers' entries electronically. |
| ABS | American Bureau of Shipping (classification society) |
| abt. | about |
| AC | Air Conditioner |
| AC | Activated Carbon |
| AC | Alternating Current |
| Acc. | Accepted, Acceptance |
| ACS (A.C.S.) | U.S. Customs' master computer system, "Automated Commercial Systems." |
| Add. | Addressed |
| AF | Advanced Freight |
| Aframax | tanker < 80,000 dwt (average freight rate assessment) |
| AIS | Automatic Identification System |
| Alk. | Alkilinity |
| AM | Anti Meridian |
| AMNI | Associate Member of The Nautical Institute |
| Amps. | Amperes |
| AMS | The U.S. Customs' "Automated Manifest System" |
| AMVER | US Coast Guard's Automated Mutual-Assistance Vessel Rescue System |
| AOR | Atlantic Ocean Region –E : East, -W : West |
| API | American Petroleum Industry |
| AR | All Risks |
| ARCS | Admiralty Raster Chart Service |
| ARPA | Automatic Radar Plotting Aids |
| ARQ | Automatic Repetition Request |
| ASCII | American Standard Code for Information Interchange (IT) |
| AT | American Terms (grain) |
| ATDNSHINC | Any time Day or Night Sundays & Holidays Included. |
| atm | Atmosphere |
| AUSREP | Australian ship Reporting System |
| Av. | Average |
| AWWL | Always within Institute Warranties Limits (Insurance purpose). |