Ad.HSVtk is a commonly used term in medical and scientific research that refers to a type of gene transfer vector used in cancer therapies. Synonyms for this term include Adeno-HSVtk, adenoviral vector carrying HSVtk, and Adtk. These synonyms are used interchangeably to describe the same concept of using adenoviral vectors to deliver the herpes simplex virus thymidine kinase gene to cancer cells, which can then be targeted with antiviral drugs. The use of Ad.HSVtk as a cancer therapy has shown promise in preclinical studies and is currently being tested in clinical trials as a potential treatment option for various types of cancers.