Pneumonia is a general term in widespread use, defined as infection within the lung. It is due to material, usually purulent, filling the alveoli.
Pneumonia is in contrast to pneumonitis, which is inflammation of the pulmonary interstitium. Of note, some of the interstitial lung diseases are termed pneumonia rather than pneumonitis. Some clinicians, including even some radiologists who should know better, use the term consolidation as a synonym for pneumonia, this is of course incorrect.
Pneumonias can be classified by:
- method of spread (a pathological description)
- radiographic appearance