| Term | Definition |
| retrospective | Characterize by looking back at the past and reflecting; related to the past. |
| retrofit | to go and install something that was not availble at the time of original manufacturing. |
| retroactive | Goes back to a prior time. |
| antibacterial | Designed to fight against or kill bacteria. |
| antonym | A word that means the opposite of another word. |
| antidote | A remedy or cure; something that works aganist a poison. |
| antihistamine | A medicine thay works against colds and allergies. |
| antacid | A substance that works against stomach acid. |