Full form of NDA: National Defence Academy

Explanation:
The National Defence Academy (NDA) is the joint services academy of the Indian Armed Forces, where cadets from three services, the Army, the Navy and the Air Force, are trained together before they go on to pre-commissioning training in their respective service academies. The NDA is located at Khadakwasla near Pune, Maharashtra.

Training:
The training at the NDA is conducted in three stages:

1. The first stage is a three-year program in which cadets are trained in basic sciences, humanities and social sciences.

2. The second stage is a one-year program in which cadets receive training in their respective service academies.

3. The third stage is a one-year program in which cadets undergo training at their respective service training academies.

Admission:
The admission to the NDA is through a written examination conducted by the Union Public Service Commission (UPSC) followed by an interview conducted by the Services Selection Board (SSB). The written examination consists of two papers, Mathematics and General Ability Test, each carrying 300 marks.

Eligibility:
To be eligible for admission to the NDA, a candidate must be a citizen of India, unmarried and between 16.5 and 19.5 years of age. Candidates must have passed 10+2 with Physics and Mathematics as compulsory subjects.

Conclusion:
The National Defence Academy (NDA) is a premier institution for training officers for the Indian Armed Forces. The training at the NDA is rigorous and prepares cadets for the challenges they will face in their respective services. The selection process is competitive and only the best candidates are selected for admission to the NDA.

National Defence Academy is your answer.