PN may refer to:
Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli.
A pneumothorax is an abnormal collection of air in the pleural space between the lung and the chest wall.
A pnictogen is one of the chemical elements in group 15 of the periodic table. This group is also known as the nitrogen family.
A pneumatic motor (Air motor) or compressed air engine is a type of motor which does mechanical work by expanding compressed air.
Pneumatic tubes (or capsule pipelines; also known as pneumatic tube transport or PTT) are systems that propel cylindrical containers through networks of tubes by compressed air or by partial vacuum.
Pneumococcal conjugate vaccine (PCV) is a pneumococcal vaccine and a conjugate vaccine used to protect infants, young children, and adults against disease caused by the bacterium Streptococcus pneumoniae (the pneumococcus).