| Acidi carbossilici | Carboxylic acid |
| Acidi grassi | Fatty acid |
| Acidi grassi trans | Trans fat |
| acidi nucleici | nucleic acid |
| acidificare | acidify |
| acidificazione | acidification |
| Acidificazione degli oceani | Ocean acidification |
| acidimetro | acidimeter |
| acidità | acidity |
| acido | astringent |
| acido acetico | acetic acid |
| acido acetilsalicilico | acetylsalicylic acid |
| acido acrilico | acrylic acid |
| acido adipico | adipic acid |
| Acido alfa-amminobutirrico | Alpha-Aminobutyric acid |
| Acido antranilico | Anthranilic acid |
| acido ascorbico | ascorbic acid |
| Acido azelaico | Azelaic acid |
| acido barbiturico | barbituric acid |
| acido biliare | bile acid |
| acido borico | boric acid |
| Acido bromico | Bromic acid |
| acido butirrico | butyric acid |
| acido caprico | capric acid |
| acido caprinico | capric acid |
| acido carbonico | carbonic acid |
| acido carbossilico | carboxylic acid |
| Acido cianidrico | Hydrogen cyanide |
| acido citrico | citric acid |
| acido cloridrico | hydrochloric acid |
| acido crotonico | crotonic acid |
| acido deossiribonucleico | deoxyribonucleic acid |
| acido desossiribonucleico | DNA |
| Acido di Lewis | Lewis acid |
| Acido dicloroacetico | Dichloroacetic acid |
| acido diluito | diluted acid |
| acido eicosapentaenoico | eicosapentaenoic acid |
| Acido fluorosilicico | Hexafluorosilicic acid |
| Acido fluorosulfonico | Fluorosulfuric acid |
| Acido folico | Folic acid |
| acido formico | formic acid |
| Acido forte | Strong acid |
| Acido fosforico | Phosphoric acid |
| acido fulminico | fulminic acid |
| acido galatturonico | galacturonic acid |
| acido gluconico | gluconic acid |
| Acido glutammico | Glutamic acid |
| acido grasso saturo | saturated fatty acid |
| Acido ialuronico | Hyaluronan |
| Acido ibotenico | Ibotenic acid |
| Acido lattico | Lactic acid |
| Acido lipoico | Lipoic acid |
| acido lisergico | acid |
| Acido mevalonico | Mevalonic acid |
| acido nitrico | nitric acid |
| Acido nucleico | Nucleic acid |
| Acido orotico | Orotic acid |
| Acido peracetico | Peracetic acid |
| Acido perossimonosolforico | Peroxymonosulfuric acid |
| Acido poliglicolico | Polyglycolide |
| acido prussico | prussic acid |
| acido ribonucleico | RNA |
| acido ricinoleico | ricinoleic acid |
| acido salicilico | salicylic acid |
| acido sialico | sialic acid |
| Acido sicilico | Orthosilicic acid |
| acido silicico | silicic acid |
| acido solforico | sulfuric acid |
| acido solforoso | sulfurous acid |
| acido stannico | stannic acid |
| acido stearico | stearic acid |
| acido tannico | tannic acid |
| acido tartarico | tartaric acid |
| Acido tioglicolico | Thioglycolic acid |
| Acido trifluoroacetico | Trifluoroacetic acid |
| acido urico | uric acid |
| acidosi | acidosis |
| acidulare | acidulate |
| acidulo | acidulous |
| Aciduria fumarica | Fumarase deficiency |
| Acigné | Acigné |
| acile | acyl |
| acino | grape |
| Acinonychinae | Cheetah |
| Acinonyx jubatus | Cheetah |
| Acinonyx jubatus venaticus | Asiatic Cheetah |
| Acipenser huso | Beluga sturgeon |
| Acipenser sturio | European sea sturgeon |
| Acireale | Acireale |
| acirologia | acyrology |
| ACK | Acknowledge character |
| Ackbar | Admiral Ackbar |
