| Abbreviation | Definition |
|---|---|
| A | auris (ear) |
| A | axis |
| a | chemical activity |
| A | mass number |
| A | radioactivity |
| A&C | Administrative & Clerical |
| A&D | alcohol and drugs |
| A&EXX | Accident and Emergency |
| A&O | alert and orientated |
| A&R | Alert and responsive |
| A/O | Alert and orientated |
| A/R | alcohol-related |
| A4A | Awards for All |
| A4C | Agenda for Change |
| AA | acute appendicitis |
| AA | aplastic anaemia |
| AA | ascending aorta |
| AA | ascorbic acid |
| AA | Attendance Allowance |
| AA | autoanalyser |