Community acquire pneumonia is pneumonia occurring outside of the hospital or occurring within 72 hours of admission to the hospital.

The most common organism is streptococcus pneumoniae also called pneumococcus. Other organisms include haemophilus influenza, legionella species, staphylococcus aureus and klebsiella.

Nosocomial pneumonia is pneumonia acquired after 72 hours of admission. There are two types. That which is ventilator related and non-ventilator related. They are termed , HAP and VAP.