NDA, or the National Defence Academy, is an entrance exam conducted by the Union Public Service Commission (UPSC) for candidates who wish to join the Indian Army, Navy, and Air Force. The exam is held twice a year and is open to unmarried male candidates aged between 16.5 to 19.5 years. The selection process includes a written examination, psychological aptitude test, intelligence and personality test, and a medical examination. Successful candidates are then selected for training at the National Defence Academy in Pune.