Student nurses are trainees in preparation for professional nursing practice. The type of training varies. In the United States, a Bachelor of Science in Nursing (BSN) or an Associate Degree in Nursing (ADN) are common options, as well as the shorter Licenced Practical Nurse (LPN) or Licenced Vocational Nurse (LVN) programs. In other parts of the world, a Bachelor of Nursing degree may be obtained. Enrolled Nurse (EN) training still exists in many countries. Some countries train nurses for specific areas of practice, including obstetrics, pediatrics, and mental health. Postgraduate education in nursing is becoming more common, although nurses undertaking such study are unlikely to be referred to as, "student nurses".