A lung disease that involves lung parenchyma or alveolar inflammation and abnormal alveolar filling with fluid (consolidation and exudation). It results from a variety of causes including infection with bacteria, viruses, fungi or parasites, and chemical or physical injury to the lungs. It is accompanied by fever, chills, cough, and difficulty in breathing. [ http://purl.obolibrary.org/obo/ECO_0007638 ]