| | ado | | adolescent |
| | ADODB | | Active Data Objects DataBase |
| | ADPCM | | Adaptive Differential Pulse Code Modulation |
| | ADRD | | Alzheimer's Disease or a Related Disorder |
| | ADSI | | Active Directory Service Interfaces |
| | ADSL | | Asymmetric Digital Subscriber Line |
| | ADSR | | Attack, Decay, Sustain, Release |
| | adtr | | A Day To Remember |
| | AEAP | | as early as possible |
| | aelf | | Artificially Engineered Life Form |
| | aelfs | | Artificially Engineered Life Forms |
| | aes | | Advanced Encryption Standard |
| | AEST | | Australian Eastern Standard Time |
| | aetc | | air education and training command |
| | AF | | Asian Female |
| | AFAGAY | | a friend as good as you |
| | AFAHMASP | | a fool and his money are soon parted |
| | afaia | | as far as I am aware |
| | AFAIAA | | As Far As I Am Aware |
| | afaiac | | as far as i am concerned |
| | AFAIC | | As Far As I Am Concerned |
| | AFAIC | | As Far As I'm Concerned |
| | afaics | | as far as I can see |
| | AFAIK | | as far as I know |
| | AFAIN | | As Far As I Know |
| | afaiu | | As Far As I Understand |
| | AFAIUI | | As Far As I Understand It |
| | afap | | as far as possible |
| | AFAWK | | as far as we know |
| | afayk | | as far as you know |
|