| aceto | vinegar |
| aceto balsamico | balsamic vinegar |
| aceto di riso | rice vinegar |
| aceto di vino | wine vinegar |
| Acetobacter | Acetobacter |
| acetofenone | acetophenone |
| acetometro | acetometer |
| acetone | acetone |
| acetonitrile | acetonitrile |
| acetosa | sorrel |
| acetosella | wood sorrel |
| acetoso | acidulous |
| acetossibenzoico | acetylsalicylic |
| acevazione | acervation |
| ACF Fiorentina | ACF Fiorentina |
| ACH | ACH |
| Acharnes | Acharnes |
| Achatina | Achatinidae |
| Achatina fulica | Achatina fulica |
| Achau | Achau |
| Achberg | Achberg |
| Achei | Achaeans |
| Acheloo | Achelous |
| Achelousaurus horneri | Achelousaurus |
| Achemenes | Achaemenes |
| Achemenidi | Achaemenid Empire |
| Achenheim | Achenheim |
| achenio | achene |
| Acheo | Achaeus |
| Acheo di Eretria | Achaeus of Eretria |
| Achern | Achern |
| Achernar | Achernar |
| Acheronte | Acheron |
| acheropita | acheiropoieton |
| acheuleano | Acheulean |
| Acheville | Acheville |
| Achicourt | Achicourt |
| Achiet-le-Grand | Achiet-le-Grand |
| Achiet-le-Petit | Achiet-le-Petit |
| achilia | achylia |
| Achill Island | Achill Island |
| Achilla di Alessandria | Pope Achillas of Alexandria |
| Achille | Achilles |
| Achille Castiglioni | Achille Castiglioni |
| Achille Lauro | Achille Lauro |
| Achille Liènart | Achille Liénart |
| Achille Silvestrini | Achille Silvestrini |
| Achille Tazio | Achilles Tatius |
| Achille Van Acker | Achille Van Acker |
| achillea | yarrow |
| Achillea millefolium | Achillea millefolium |
| Achilli | Achilles |
| Achillobator giganticus | Achillobator |
| Achim von Arnim | Ludwig Achim von Arnim |
| achiro | acheirous |
| Achitofel | Ahitophel |
| Acholi | Acholi |
| Achrafieh | Achrafieh |
| Achroia grisella | Lesser wax moth |
| Achslach | Achslach |
| Achstetten | Achstetten |
| Achterwehr | Achterwehr |
| Achzarit | IDF Achzarit |
| Achères-la-Forêt | Achères-la-Forêt |
| ACI | American Automobile Association |
| aciclico | acyclic |
| Aciclovir | Aciclovir |
| acicula comune | Venus' comb |
| Aciculare | Spicular |
| Acid Drinkers | Acid Drinkers |
| Acid house | Acid house |
| Acidi carbossilici | Carboxylic acid |
| Acidi grassi | Fatty acid |
| Acidi grassi trans | Trans fat |
| acidi nucleici | nucleic acid |
| acidificare | acidify |
